Which value should be selected in: “Manage common options for payables and procurement”

Summary: In the task: “Manage common options for payables and procurement” there is a parameter: “Accrue Expense Items” in this parameter 3 values are managed: Blank - At receipt - Period end.
The question is: Which value should be selected in: “Manage common options for payables and procurement”

Content (please ensure you mask any confidential information): In the task: “Manage common options for payables and procurement” there is a parameter: “Accrue Expense Items” in this parameter 3 values are managed: Blank - At receipt - Period end. Depending on the selected value, when creating a PO at the Schedules line level, the system enables the flag: “Accrual at receipt”.