Let me explain.
First, you dont need math for that.
Second, roblox has this bug that if you join the same server at the same time with someone, the game thinks its just one player and accidentally lets them both of them in. There is another way to do that though, but its very rare. For an example: someone joins a game, and the game (join script of roblox) thinks that no one joined, so they dont consider that player as of course, a player. This causes the game to bug out and allow more than the max players.
Thanks for coming to my HR_Nerd talk
(If your gonna ask, yes. HR_Nerd is my display name.)