AR RecBalance RDD Calculated Field where is the data coming from?

I have two calculated fields in the AR RecBalance report data definition that I am looking to understand what data is used to populate the field in the report.

From the ARMovement data source Epicor has created the following two calculated fields: DiffPeriod and RepBalanceAcct. Does anyone know what fields or calculations are done.

The report show …4000 for the Rep Balance account field - and I can only assume that it should be displaying the full GL account number

The Diff Period is a logical field - report expression is =iif(CBool(Fields!DiffPeriod.Value)"*’
So the report is showing *

TIA,