Availabilities and Common Availabilities
Common Availabilities is to define time slots of doctor availability, shared by all doctors, while each doctor could have his or her own availabilities settings. When creating an appointment, the time slots of doctor availability will affect what time slots available in the Slot dialog. Also in the calendar view of appointments, unavailable time slots are grayed out.
When editing an appointment, it is allowed to workaround the availabilities settings through defining the start time and the end time directly.