If you'd like to offer appointment times on an increment smaller than 15 minutes, you can update your calendar increment to allow that. That way, rather than allowing appointment times on the quarter hour only (4:15, 4:30, 4:45, 5:00, etc.) you can allow 5 minute options (4:05, 4:10, 4:15, 4:20, 4:25, etc.).
To set your calendar to the 5/10 minute increment, follow these steps:
Click on the three lines in the top left, and choose Settings
Select the "Policies" tile
Choose the "Appointment Policies" tile and select the 5/10 minute increment
Then if you want to update any service durations, clean-up time, etc. to 5/10 minutes, etc. you can do so by returning to the navigation menu and selecting Settings, and then clicking the "Services" tile.