Recalculate user attachment quota's

[nylyon]

It was either add storage or mogrify the existing images.  I chose mogrify to reduce all but the past 3 months.  Now my question is how can I recalculate the user usage sizes?  Example: my members are limited to 16MB of attachments.  After reducing the image size at the Linux level, I want to recalculate the users to accurately reflect what they are using, so if they were using 16MB before, after mogrify they may be using 10GB, but their user record still reflects 16 right?