How do I add buffer times to my appointments so that I don't get booked out?

EDIT: As at 1st Feb 2019 - we have before and after buffers! Video tutorial below:

As at September 2018, we do not have a day limitation, however, what you can do is limit the minimum notice time you need to book an appointment and also time increments in which the appointments can be booked.

Minimum notice time = you can't book me with less than x minutes notice
Time increments = you can only book me 15, 30, 45 or X minutes past the hour

So you can limit 8 appointments a day for example if you have working hours between 12 and 8 with a 60 minute increment.