BEags,
Quite incorrect... I am one (new generic brevet 'n' all), and there is no requirement to tell ar*e from elbow!
But in all seriousness, distance x speed x time is a big player. If you're fairly quick and accurate with numbers you should have no issues. As discussed previously, you will end up sitting the full battery of tests which will also include memory and hand-eye coordination. The best advice I can give is brush up on mental arithmetic.
Good luck, and PM me if you need any other advice!
FM