You can definitely change the time intervals in which clients can book appointments. For example, if you'd like clients to book on the hour or you'd prefer them to book in 15 or 30 minute intervals, this is where you would edit that feature.
Go to the Settings tab on the left side menu.
Under Your Settings click on Booking Settings. This will open up your booking settings options on the right side of your screen.
On the list, fourth line down will be where you can pick the time interval for clients to book appointments.
Click on the drop down arrow and a new window will open where you can choose the interval you would like.
Hit the Save button at the top right of the page and you're set.