BA2039 16/12:2021
As you see there are 7 free seats in FLUB and 3 in CW. On top of that, the 7 allocated in FLUB will most likely be status passengers reseated from CW and their previous seats are still shown as occupied. I discovered on my last flight that BA do this. Either that, or those 7 in FLUB are you and no CW status passengers have been reseated yet, but that is less likely.
So, in all 17 spare seats, or still 10 seats on top of your booking. Don't worry.