Now this may have been explained before (apols if it has) but how can Bucks allocate ~ 300 places out of ~900 appeals without knowing any of the numbers at the time of the appeal!
Surely they must do some sort of pre-filter. It makes no sense otherwise. (I am struggling to get my head round this).
Something absolutely VITAL to bear in mind is that the Appeal Panels are INDEPENDENT by law of the local authority. The Panel members don't have any interest in how many places the authority might have. In theory, every single appeal could be upheld by the Panel (which would create a huge headache for the authoirty, but none at all for the Panel members!).
Before, during and after the appeal (at least, not until several months after) the Panel has NO IDEA WHATSOEVER of how many successful appeals there have been. They consider each case, in isolation, on its individual merits.
Hope that reassures you!