Every morning around 10 a.m., the District publishes its daily tally of new positive COVID-19 cases. If you happen to follow the numbers, you’ll know that there were 152 new reported positive cases last Thursday, 135 on Friday, 171 on Saturday, 81 on Sunday, and 147 on Monday.

That list of numbers tells a scattered story. D.C.’s case count appears to be jumping all over the place — not exactly positive news for a restless populace waiting for (among other things) those numbers to drop so we can get back to some semblance of normalcy.

But on Monday D.C. officials had a very different take: they said the city is actually in the midst of an eight-day decline in cases. (NBC 4 reporter Mark Segraves was the first to ask about this.) That’s significant, as the city is watching for 14 straight days of decline as it makes decisions about reopening the city.

So, what gives? Are cases jumping up and down, as the public data seem to suggest? Or are the rest of us just missing something that D.C. officials know?

It’s both.

While the raw positive counts published daily have become a stress-inducing metric for many — Are we going up? Are we going down? — D.C. officials said last week that those numbers aren’t the only thing they’re looking at. Instead, they’re focused on what they say is “community spread” of COVID-19, which is measured in a more nuanced way than simply reporting new positive tests on any given day.

Dr. LaQuandra Nesbitt, the head of the D.C. Department of Health, explained that the daily tally of cases is just an accounting of positive tests. But that’s not wholly helpful in understanding the where, when, and how of COVID-19’s transmission through the city.

“A much better indicator… is when we get those new lab reports, we’re able to see what the actual symptom onset for those individuals are. So if you really want to appreciate the disease patterns or new infections in the community, you can actually look at the symptom onset for the District,” she said during a press conference where Mayor Muriel Bowser announced she was extending the city’s stay-at-home order through June 8.

By the time an infected person has tested positive for the virus, they may have been symptomatic for days. The Centers for Disease Control and Prevention says the average lag between symptom onset and a positive test is four days. (This handy graph of case data from Michigan shows the delay in action.) There are also issues around when tests happen (fewer on the weekends) and how long results can take to come in.

That’s why knowing the symptom-onset date is critical information for health officials, since they generally know what the virus’s lifespan is.

“My decline in 14 days starts from knowing when people started not to feel well versus when test results were reported,” said Nesbitt during a phone conference with members of the D.C. Council late last week.

Additionally, not all positive cases are created equal. If you’re a resident at a nursing home or an inmate at the D.C. Jail — both hot spots for the virus — testing positive for COVID-19 means a lot for your immediate neighbors, but not necessarily very much for everyone else outside the walls of those institutions.

“We take the rate of decline for people moving around the community versus people who are in confined spaces,” Nesbitt told lawmakers.

So, measuring based on the onset date (versus the date someone tests positive) and controlling for cases in congregate settings gives D.C. officials a better means to understand how the virus is progressing through the city. And that can look very different from the raw number of cases published on a daily basis.

“This is not a new methodology. The Epi Team has been collecting this information and using it to inform the Epi curve all along,” said D.C. Health spokeswoman Alison Reeves in an email, referring to the “epidemic curve,” which has long been used by health officials to measure outbreaks over time.

None of these numbers are public, though, which has led to some confusion around D.C.’s actual decline in cases — or, rather, “community spread.” On the same day that Nesbitt explained this methodology to reporters last week, she also detailed it to councilmembers, who questioned how a then-five-day decline in community spread had been calculated.

When asked today why these more nuanced numbers aren’t made public, D.C. Deputy Mayor John Falcicchio said it’s because they can shift quickly; someone who tests positive one day can remember the next day that they came down with symptoms a week earlier, giving health officials the data they’re most interested in.

Of course, this metric — the 14-day decline in community spread — is just one of a number of metrics D.C. officials are using to determine when it’s safe to start a phased reopening. They’re also looking at the rate of transmission, or how many people each positive person might infect. Experts say the ideal rate is less than 1; as of this week, D.C. has been below that threshold for more than three days, which is where officials say they want to be.

There’s also availability of hospital beds and personal protective equipment, as well as contact-tracing capabilities and testing of priority groups like first responders, at-risk groups, or people showing symptoms.

“We continue to have our hospital usage trending in the right direction, so we’re on track,” Bowser said on Monday. “We are eight days towards 14 days of decreased transmission, our testing and hospital usage is also on track, and our tracing capability is almost where we need it to be.”

While Bowser wasn’t willing to declare victory, she has said she’ll follow the data on whether to start a phased reopening before the stay-at-home order expires on June 8. And later this week her ReOpen D.C. Advisory Group will issue its first recommendations on what reopening the city would even look like.

What will tomorrow bring? You’ll know at 10 a.m., when D.C. releases its new tally of positive cases. But even if that looks bleak, don’t forget: you’re not seeing the same data health officials are—and that could make all the difference.