CRM Settings / General Settings / Pupils/Parent Meetings / Basic Settings / Minimum Time to Cancel/Modify a Meeting (in hours)
Here you define the minimum number of hours before a user can cancel or modify an already scheduled appointment. E.g., if you set here the number 8, then a parent can cancel or modify a scheduled appointment with a teacher only until 8 hours before the scheduled meeting time.
Note that if you set 0 here, there is no control.
