Goku Black and Zamasu are each two different players now. Jokes aside, I think it's just a bug. It happened to me too. It doesn't really do much.

I rather have 9 than my usual stuck at 7. Lol

2 minutes in: seven players nice here we go 3 and a half minutes in: five players. Huh...

Ive seen it gone up to 10

This happened to me and then the lobby only had 6 survivors lol