The booking schedule is split into time slots called periods, which default to 30 minutes. You can change these to as short as 5 minutes, depending on what works best for the bookings at your facility or with a staff member.
For example, if you wish to offer 15-minute, 45-minute, and 1-hour bookings, setting the period to 15 minutes is a good choice.
You can change the booking period's under:
Settings > Booking and Classes > Facilities > Category List
Settings > Booking and Classes > Staff > Category List
Just click the [Edit] button next to the category you want to update, and adjust the period length there, this will apply the change to everything under that category.