There may be gaps in your online bookings due to your online bookings preferences. If you want to make sure there are as few gaps as possible, make sure that you have "Dynamic" selected for Appointment Scheduling (this will allow appointments to be made in open slots in your schedule, as opposed to fixed time slots only).
To enable dynamic appointment scheduling:
Click Personal > Locations.
In the Hours, Profile and Book Preferences section, click the Expand (+) icon next to the name of the practitioner whose preferences you are changing.
Click the Edit (pencil) icon to the right of "Online Bookings and Profile Preferences".
Under Appointment Scheduling, select Dynamic.