I just assume the numbers represent a subset of people who are regular moviegoers or something.

Not sure about that, I know a number of people who have gone (including myself), and I don't think most of them are regular moviegoers (I'm certainly not, it's been like like 6 years since the last time I can remember). Admittedly, I wouldn't have gone and would have waited for it to drop for free on the internet if someone hadn't talked about going, but even that isn't something that really happens to me normally