Hello @Robert339,
Did you do the synchronising by clicking on "Export calendar" or on "Import calendar" on the Airbnb website?
If you imported the other stie's calendar to Airbnb then it might be possible to delete the imported calendar from the listing you don't want synchronised.
Click on "Host" and then on "Manage listings" in the menu. Then click on "Calendar" for the listing that you don't want synchronised. Now scroll down to the "Sync calendars" section. If there's a little bin symbol on the "Import calendar" line click on on it to stop the synchronisation.
If the synchronisation was done by exporting the Airbnb calendar and importing it to the other site you could check on the other site to see if it has two calendars imported. If it has, delete the one you don't want.
If the above doesn't work you could try removing the synchronisation and doing it again.
Steve.