When you establish a two-way Google Calendar sync or a one-way Full Slate to Google sync, you'll see a warning that indicates the action cannot be undone. This is because the synchronization process actually copies events from one calendar program to the other, and the copied events will remain in the second program even after the sync is removed. The only way to remove the events is to manually delete them one-by-one (though there is one exception when you first establish the sync, when you can reach out to us and we can remove the initial batch of synced events in Full Slate).
To be clear, you can remove the sync at any time so that future events no longer sync between the programs, but the previously-synced events will remain.
Please note the one-way sync from Google Calendar to Full Slate acts as a 'read-only' sync, so all synced events will be removed from Full Slate when you remove the sync.
We recommend that you establish only one two-way sync on any given Full Slate schedule and on any given Google Calendar. Otherwise, there is a good chance you will get duplicate events across schedules. To keep this from happening, you'll want to use different Google Calendars for each Full Slate staff schedule; it's okay if each of the Google Calendars are in the same Google account. For example, you can sync Joe's Full Slate schedule with Joe's Google Calendar, Tamara's Full Slate schedule with Tamara's Google Calendar, and so forth.