Allow specific times to be available
Because the service is available from 09:30 when I put one hour appointments in the appointments start at 10:00.
If I change it to half hourly time we lose at least one available slot because people create gaps unintentionally
We also can't book breaks
Mark B commented
If I have a 90 minute gap, and 60 min/30min sessions... I would want to specify that the 30 minute session CANNOT inhibit a 60 min booking if the sum of the remaining time in the session is 60 mins.
I.e. If the 90 gap was empty, the 30 min must go at one end or the other.