I think a CF of 100K would be rare, even in the bigger cities. I'd be surprised if more than a few orgs had a CF that big. LA for a long time had way more Scientologists than anywhere else so I'm sure some of those orgs have a big CF, but those orgs are the exception. I'm not sure what the average CF size is for an org, but I'd guess way under 100K, 50K? 30K? less? It's also a meaningless stat, most of those names are just someone who bought a book 30 years ago.
Before the pandemic I thought Scientology numbers were 20K-25K, maybe 30K on the high side but not more than that. It's hard to say how many they lost exactly, and how many they'll be able to get back now that they're open. I think an estimate of 15K is a good guess. If they're claiming 30K IAS members the real number is half of that at best.
I think the stat should be something along the lines of who has completed a course (any course) in the last 3 years and how many staff/SO. A large number of OTs go back to Div 6 to do the various book/lecture courses so if you start looking at only those who have done major services you're going to miss a lot of them. Maybe something along the lines of who has consistently been at a roll call would work.
I've thought about it a little bit, I'm sure someone in management knows the numbers and at least has a good idea of how things are, but I'm not sure that even they have an accurate count. The main stats I think they'd watch as far as number of Scientologists would be number of staff/SO, BIS and event attendance. Number of staff/SO and event attendance they probably have accurate counts on, but I'm not sure they have an accurate count on BIS. When stats get reported uplines they just report numbers and each org reports its own stats. So for a D & F they might report up 200 each for BIS. Now management thinks Org X has 400 BIS. But really there is a lot of crossover, nothing prevents someone from being BIS at both orgs, so 100 of that 200 are on course at both orgs. The real weekly BIS for the org is 300. I'm not sure that Scientology is smart enough to track things like sign-ups, completions, etc. to get the real count. If they're tracking BIS just based on reports from orgs, and BIS is an average of 10K or whatever, I wouldn't be shocked that if you started to dig into that 10K number you'd find out it's really 7K or something.