To verify just how large the data in the item number field is, use the Count(field) function in a formula (in the detail section) to verify the lengths of the item numbers. My guess is that one item in the data set has a length of less than 6 characters, thus causing the problem. You could also create a formula to label all of the records where this is true [If count(Item number)<6 then...].

When you determine the item number causing the problem, you will either have to modify your formula with the subscript to incorporate this data, or create a selection formula to dis-allow item numbers <6.

You probably should temporarily delete this formula while testing this out, so that the report can print.