Why are available times different between Site Administration and the Customer View?

The functionality of the calendar on the customer view is different than that of the administration calendar. The customer view does not show all open slots. The slots on the customer view represent available start times that would fit the appointment. For example, if the administration view shows that a staff member has availability between 9 am and 11am. The slots in the customer view represent available start times for the appointment. In this example using a 1-hour duration service, the only slots that show open are from 9 am to 10am. 10:15 to 10:45 does not show as available to book as the hour-long service would end at 11:15 and overlap into the next 11 am appointment.