There is a subscription in the Administartive/Credit hold status. After each daily billing there is a billing order for resource overusage for 1 day duration. Why does it happen?
There are resources which are supposed to be billed when overused even if the subscription is stopped (e.g. OACI stopped resources), refer to the documentation for more details. Billing orders are generated daily (not one order at the end of the billing period) because of the bug with id #PBA-70636 ("Subscriptions on hold get divided Billing orders for overusage instead of one BO for total amount").
Update to BA 6.0.8 or above. After updates installation subscription will be billed only once, not daily.