To my knowledge from working at a medical facility, they have to submit all tests to the state for numbers. I've seen plenty of people who have been negative decide to test again weeks later because they were around someone with covid. Also, all positives need a negative test before they can go back to work. So a positive test is an automatic 2 tests per person. Some fail and need a 3rd as they're still positive or the facility fucks up and didn't realize the patient is still in the 14 day window of first test.
It's a huge mess. There is no way the numbers are accurate. I'm not sure if each state has it's own rules on tests submissions, but my state, you have to send in all testing you do, daily.