really it depends on which rooms game you play
Original Rooms? Just 2 entities, A-60 and A-200
Interminable Rooms? Over 30 entities, 3 sections (4 if you count the April Fools U section), some entities with unique mechanics (E.G. A-150 and A-100 checking lockers in the most recent room, A-200 and A-332 going backwards when a player exits their hiding spot, A-300 being able to spawn entities, etc), and lots of other shit like being to hide under tables and some blue lockers.