If you haven't entered any reservation, nor blocked the availability on the rooms, the channel manager is going to reopen all your rooms on the online agencies.
Bear in mind a couple things:
1. Xotelia is going to be master on all the online agencies meaning Xotelia is going to update all the rates and availability on the online agencies.
2. No reservations will be imported from the online agencies.
3. Even though Booking.com has already sold your room, Xotelia will tell them you have another one of the same type on sale. And nothing will stop this from happening.
So, once again, one way or another, block the dates in your calendar before any synchronisation is done.
You can either create them manually, import them, or block the quantities in the calendars.