If we assume vast majority of Internet users are Smartphone users. There are total of 4.5B Smartphone users, China has close to 1B. That is 2.7B out of 3.5B.

So Yes, roughly 77%.

And with IG and WA they make 3.2B out of 3.5B, ~93%

Surely there’s overlap between the users? Or was that factored in already.

Already Factored in. In other words, 90%+ of Smartphone users outside China has at least one of the Facebook App installed.

And growing.