Limit Attendees To Capacity
Prevent overbooking by restricting the number of attendees to the room’s set capacity.
Limit attendees to capacity
This feature restricts users from adding more attendees than the set capacity of the room.
If your meeting has attendees that are joining remotely these users are excluded form the check along with any users marked as 'unknown' in the Anticipated location section.

If a room has no capacity set, no limit will be enforced even if this feature is enabled.