How bookings work — Classes, and anything shared

Twenty people at one yoga class is twenty rows at the same time with the same instructor. On an ordinary appointment table that reads as nineteen double-bookings. Give the view a capacity — a number saying how many the session takes — and it counts seats instead. Bookings sharing a slot stop being flagged, and only real problems remain: a class with more people in it than it holds, and one instructor booked into two different things at once.