Getting the contents of a repetition in a repeating field
To find the contents of a particular repetition in a repeating field, use the GetRepetition function (see GetRepetition function) or use square brackets [ ] as array operators (see below).
repeatingField - any repeating field
number - the field repetition number
Data type returned
text, number, date, time, timestamp, container
Returns the contents of the repeating field specified by number.
ParcelBids is a field defined to repeat with ten values and contains the values 2500, 1200, and 1500.
ParcelBids[2] returns 1200.
ParcelBids[5] returns nothing.
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
About formulas
About functions
Defining calculation fields
Using operators in formulas