Sometimes, you want to create a reminder just for yourself in your Google / Outlook calendar and you want that time available for external bookings. Sometimes you legitimately want to block out that time.
When you create an event, or click on an existing event, navigate to the drop down where it says "free" or "busy" and toggle your option. In Google calendar the dropdown is next to the briefcase icon.
Toggling this feature will adjust whether you can be booked through Cogsworth.