This is decided by the system the "Playing Time" + the Time the buggy is required before tee time & after finishing the round. These settings can be found in "Tools">>"System Configuration".
EXAMPLE:
If you make a booking at 12:00pm which has a buggy, your system Playing Time is 4hrs and your "time buggy is required before tee time and after round" are 15 minutes each, the system will show that you have one fewer buggy available 4hrs and 15mins before and after the 12:00pm booking.
