This function means that if a borrower returns an overdue book, their system privileges are suspended for a number of days after the event.
If you want to 'fine' patrons by suspending their account, the rules for suspensions are set in Circulation and Fines Rules.
You can enter the number of days their account should be suspended in the 'Suspension in days' field. Please note, this can only be set for the Day unit, not in Hours. So, if you want to suspend the account by 1 day for every day that an item is overdue, set Fine charging interval to 1 and Suspension in days (day) to 1.
You can also define the maximum number of days a patron will be suspended in the Max suspension duration setting.
If the patron has more than 1 item overdue and you want to allocate suspensions to each overdue item:
Set SysPrefCumulativeRestrictionPeriods = Cumulate