The numbers don’t add up where I live.
The 8.5 million is the global number.
I don't see how you can determine whether there is still growth in Brazil, Botswana, or Bolivia because attendance is down at the 3 or 4 Kingdom Halls you are familiar with in your small corner of Canada.
The WTS is scrupulous with their numbers. There are definitely 8.5 million persons who "turn in a time report" every month, which is what the number represents.
How many of them "really" believe it? How many of them are engaged in "secret wrongdoing" that would get them disfellowshiped if exposed? How many are trapped and just going along because they don't want to lose family, friends, business contacts, or pretty much the only way of life they have ever known?
Those are different questions, of course. "True believing" JWs are certainly much less than 8.5 million, but there is no accurate way to measure what that number would be.
But 8.5 million "turning in a field service report"? Certainly true.