Problem with Disk Quota

Hi,

I have a reseller account which cannot change the quotas of his users without getting this error:

Sorry you cannot modify this account because doing so would exceed your disk space allotment. You have exceeded your disk space allotment by 9 Megabytes!

The number of megabytes over is always the amount that you would try to change it by.
Using root, I can modify the resellers accounts and change the quota no problem. The reseller has a quota of 15GB of which about 1GB is being used. It shows that in root but if you login to the reseller account it shows something different. I have attached a picture.

Any suggestions would be helpful.. this totally seems like some crazy glitch but perhaps I am wrong.