$2000 is the maximum amount to be deducted each time. This is normally set to the potential maximum amount so that you don't have to renew the authroisation form every year. And this standing order is upto year 2012 i.e. P6 for the kids.
1 wrong answer means 33 marks is quite serious. Which question is that?
There are really some questions with 3 marks while some are of mutiple of 3 marks e.g. 3 x 4 = 12 marks. I remember there is one page (in the front) that worths total 48 marks.