The maximum number of open bookings for a user. A booking is considered 'open' if it lies in the future. If the user has reached the maximum number of bookings, a new booking can only be made when an existing booking expires (or when a booking is cancelled).

An entry here overrides the value entered for a user group, which is displayed in a greyed out field to the right of the entry field. In addition, the user's current number of open bookings is displayed in the "open bookings" field.