What is the result type specified for your calculation, Text or Number?
Using GetNthNumber in a "chain" like this can rapidly reach a system resources limit on iOS devices so you might consider using a running total summary field in place of this calculation field to compute a running total of Gain.
Result type is number.
IOS is working perfectly.
It is only Mac (Top Left) that is displaying ?
Which doesn't change the fact that a running total summary field would seem a far simpler way to get this same running total.
I see no reason for the ? result from here. I think I'd run a recover on the file just to see if the recovered copy had the same issue. A recovered copy will have all rebuilt indexes and your calculations fields will all re-evaluate from scratch so that might clear the issue.
Thanks for your advice.
I am a new convert from Excel.
Field type "Summary" solved it.
I used "Running total" Summary field Check Box.
I hadn't dug deeper enough into Summary options until now.
Thanks again for help!