For semester subscriptions there is the possibility to cancel lessons up to 6 hours in advance in the Student Portal. This automatically assigns a “Make-Up Credit” from the system and frees the unit for other students.
If you have a make-up credit, you can sign up in the calendar up to 4 hours before any given free slot. This is done according to the “first come first serve” principle.
Free slots will be visible in the calendar if you have one or more make-up credits (and if someone cancels a unit in time)
This also means that you can ONLY redeem make-up credits on freed slots, because they take place during my scheduled teaching hours.
Please understand that you cannot use make-up credits outside my regular schedule. Furthermore, unused make-up credits expire after 365 days.