Unable to change Reseller's (John Doe) Limit for disk space. The following error is shown when trying to change the limit:
PLESK_ERROR: Unable to set the required resource usage limit (25000 MB Disk space) because the new value is less than the amount of resources reserved for your customers or used by yourself (38116 MB Disk space) .
Plesk calculates the allowed values for resellers disk space limit using sum of limits seted in already created subscriptions for this reseller. It's not possible to set reseller disk space limit lower than sum of subscriptions' disk space limits.
Reduce the limits for existing subscriptions in such a way that sum of disk space limits does not exceed the value for reseller:
Log in to Plesk web interface.
Go to Resellers > John Doe > Subscriptions
Open an appropriate subscription and click Customize link on the right pane (Account section):
Set disk space limit in the Resources tab: