If you select the list type Check credit limit you can make the following selections:
Only Customers with Exceeded Credit Limits
If you select this setting, only customers with a negative value in the Difference column will be shown. In this column, the credit limit is compared with the order backlog, accounts receivables, etc, (depending on which alternative you have selected to check against in the abovementioned setting)
Consider Grace Period
This setting affects what will be shown in the Of which dued column. If you check this setting, only invoices with delayed payments - when you have taken the grace period into consideration - will be shown. The grace period is configured in days in the Settings procedure.