The following fields are required when importing credits with an Application Restriction:

Record Import ID or Record ID
Transaction Date
Post Date
Billing item
Credit Distribution amount
Credit Distribution debit account number
Restriction to use
Determine Restriction Using

The Restriction to Use field is looking for the Restriction ID of the application restriction created in Configuration, Application Restrictions. The Determine Restriction Using is looking for a date that falls within the valid date ranges of the Application Restriction.