Capacity is not one number. Each activity takes a fixed group per session with a fixed instructor, so a site that sells tickets against a total figure ends up with forty people queuing for a course built for twelve.
Consent forms are the arrival bottleneck. Signed digitally in advance, including a parent's consent for under-eighteens, they turn a queue at the desk into a group that starts on time.
A cancelled morning has to be rescheduled in one action. Contacting sixty people individually is not possible before nine o'clock, and the difference between a credit offered immediately and a refund demanded later is most of the day's revenue.
Rotas follow the activities, not the calendar. Which courses are open decides how many qualified instructors are needed, and a wet forecast changes that number the evening before.