CRM Settings / General Settings / Pupils/Parent Meetings / Basic Settings / Maximum number of meetings between two entities (e.g., a parent and a Lecturer) per Academic Period
Here you can define the maximum number of meetings that can be booked between two persons during the academic period. (e.g., if you define 4, then a parent may book up to 4 meetings with a Lecturer during an academic year).
Note that if you set 0 here, there is no control.