Thanks for the feedback CAM. It is not being used for AM/PM so there should be no registration issues.
Their argument is that even though they are adding a number instead of a '/' it is still recording attendance at lessons, just adding an extra layer of information. The fact that the teacher has given them a number in the lesson means they have attended the lesson and whatever the number is gives an indication of their attitude in lessons.
We carry out a similar process for our reports already as yourselves, a staff judgement on the student's attitude to learning included on their report for each subject.
I think I will give it up as a bad job. I can extract the information via a report to excel and carry out some analysis that way but hoped I might be able to do it directly within a marksheet. I suppose thinking about it I could do the analysis in excel, create some aspects in SIMS to suit, then import to SIMS. This way I could include on marksheets and reports.