Make sure to Display Data for Index# and set the value. The value will be equal to the Dim's on the item under the Dim's tab, 1=A, 2=B, 3=C etc. It appears there is not a Calculated Field print object in addreports but you can add another Item Dim List field to add the Calc. Once you add the Calc, you can choose to not output the other values. What I find helpful, rename the print object, Item Dimension List #1 (calc), this lets me know it's being used for a calc when I have to come back and modify or troubleshoot the report. Same goes for print objects I use for filters, adding (filter) to the print object name.