One of my customers shows disk quota Used 0 MB of 0 MB limit, but actually has about 5MB.

The disk space problem appears when a check-paying user tries to increase the disk space quota. Disk quota resource is changed on the add/remove basis. The old disk space quota is removed and the new disk space quota fails to be created but fails, because this would go beyond the credit limit. The solution is to increase this user’s credit limit and then restore the disk quota resource.