By default, we recommend working with a check-in system. When checking in on site, a credit can be deducted directly. Various settings are available for check-in. These are described in detail here: Check-in and access control explained
Alternatively, it is possible to create bookable appointments for the free training units in the timetable. See also: How does the online booking for individual appointments work?
If the pass should also entitle you to attend other classes (e.g. group fitness), please note that passes are defined for the same category.