Both of them???
Each exam may only ask 75 questions, but there will be a greater range of questions that can be asked for that particular subject. For arguments sake, lets take Meteorology, if memory serves me correct there were 100 questions, but that does not mean that the CAA only ask the same 100 questions time after time after time, they have 100's of question they can pick and choose from, so each month each paper will be different.
The website/question banks try to give you as many questions as possible that
could be found in the exam therefore offering a wider range of material to revise from.
Hope this makes sense!? And good luck with your studies
A08