When you book a Focusmate session, the event details will be generated and sent to the email address associated with your Focusmate account.
Some calendars, such as Google, have a setting that allows you to automatically add invitations to your calendar.
These settings are managed in your calendar, however, and not by Focusmate. Any settings you modify will be applied globally to all invitations that are sent to your account.
If you're using this feature, you can also set a filter for all emails sent by firstname.lastname@example.org so they skip your inbox and get categorized as something else. This way, events will still be added to your calendar, but the emails won't clutter your inbox.