Translation for B/S vs I/S accounts in FCC

We are working with external auditors to explain them the translation logic in FCCS. We enabled the default translation method which takes the average rate and applies it to all Balance sheet and Income statement account and calculates the FCCS_Mvmts_FX_Opening, FCCS_Mvmts_FX_Movement ONLY for the Balance sheet accounts to plug the FX_opening and FX_movement differences.

FX on Opening = FCCS_Mvmts_FX_Opening = (FCCS_OpeningBalance * (CM EOMRate – Prior Period EOMRate))

FX on Movement = FCCS_Mvmts_FX_Movement = (FCCS_Mvmts_Subtotal * CM EOMRate) – (FCCS_Mvmts_Subtotal * CM Avg Rate)

This is only done on the Balance sheet accounts and not on the income statement accounts. How does FCC determine whether it is a B/S vs I/S while applying this logic. Is it based on the account type ( Asset, Liability, Equity Vs Revenue,Expense) property or is it based on the location of the account under the Balance sheet hierarchy? We have gone through the documentation and it is not clear enough to show how this will be determined by FCC.