How does double booking prevention work?
Here's how to ensure you don't accidentally get double booked:
During the setup of your Bookable Schedule (or if you edit it after), go to the second section, called Availability. Under Check for Conflicts, select any calendars you use that might have events on them you'd be busy for:
Finish the setup and save, or click on Done Editing to save the changes
That's all you have to do! Any Bookable meeting times that conflict with events in your selected calendars will be removed from view, so the recipient can only book times that do not conflict with other events. It will also update in real time - so if a conflicting event is added to your calendar after you sent the Bookable Schedule to someone, when they open their email they won't see any options that conflict with that newly added event.
If you're seeing times get booked that should not have been available, it's most likely one of two things:
There's a calendar you use that wasn't added to the Check for Conflicts section, OR
There's an event in that calendar which was set as Free rather than Busy.