What is the difference between time intervals and the accuracy of the calendar?

Accuracy of the Calendar

The accuracy of the calendar determines how detailed entries appear in your calendar's week and day view. You can adjust this setting under User Profile > Calendar Settings. It only affects how the calendar is displayed.

Time Intervals

Time intervals determine at what spacing customers can book appointments. With an hourly interval, customers can only book on the full hour; with a 15-minute interval, they can book every 15 minutes, e.g. 10:15 AM or 10:30 AM.

You can adjust the time interval in the "Time Intervals" section under Calendar Settings > Booking Settings. Here's a direct link to your calendar's booking settings.