The typical offer will account for the majority of offers, and the other will mainly be when someone takes an A-level that has little bearing on their aptitude for their degree subject. For example imagine someone applying for maths who takes Maths, Further Maths and French and applies for maths, the maths department might not care what the french result is. For Geography that is unlikely to be the case no matter what you take, such is the broadness of the subject.
All you can do is try to write a really good personal statment and hope for the best.