Aging Reports (AR251) - F.O.R.

Basically, correct. F.O.R. stands for "Funds Outstanding Ratio", and is a measure of days past due.

This is from Lawson documentation:
The FOR is not calculated for the future and current periods because the FOR applies only to invoices and debit memos and is always calculated using the invoice date. The FOR is calculated as follows: 1) for each transaction, multiply the days outstanding by the open amount to calculate the receivable days; 2) Add the open amount of all open items to calculate the total open amount; 3) add the receivable days of all open items to calculate the total receivable days; 4) divide the total receivable days by the total open amount.