try this if index() >window_max( index()) -15 then sum([Number of Records]) end
it returns this in your viz
If this posts assists in resolving the question, please mark it helpful or as the 'correct answer' if it resolves the question. This will help other users find the same answer/resolution. Thank you.
In addition to directions provided by Jim Dehner find my approach as reference below and stored in attached workbook version 10.2 located in the original thread.
1. NM M1. Index: index()
2. NM M2. Last: LOOKUP([NM M1. Index],last())
3. NM P1. Last N
4. NM M3. Display: [NM M2. Last]-[NM P1. Last N]<=[NM M1. Index]
5. Drag the required objects to the indicated locations.