In your Bookeo account, you can set the "granularity" of the calendar. This determines how many cells per hour are displayed in the manager calendar, and what times customers can make a booking for.
1. Go to Settings>Booking Preferences
2. Go to the Time resolution section
3. From the scroll down menu, select the:
- Time resolution for you  (from 5 min to 1hr)
- Time resolution for customer  (from 5 min to 1hr)
In this settings example, your Bookeo calendar will have a 15 min grid
and your customers will only be able to book at 30 min intervals