Thank you very much for your help+ (including screenshots is really nice of you).
I now undersatnd that the order in which the questions appear in the grades grid is the order in which I inserted the questions by category and the sub order of appearnce of the question within the test.
This is intellectually interesting but why isn't there a way of ordering the grid in the order the students saw the questions (much easier for regrading)!
Thanks again!