According to the release notes for 2.4.0 (2014-02-25) we are able to adjust users quota limit. However I do not see that as an option on the users account. I can create a new group and set a new quota limit on the group, and assign the group to a user or assign a quota to ALL users in the group. There doesnt seem to be a way to set a specific users quota. New Feature: Quota Support - having the ability to limit the number of Megabytes a user, group or domain can store on the system. I am on 3.2.4 so I am well beyond the 2.4.0 release.
The recommended way is configure Per User Quota: "Admin > Groups > Edit user's group > Size & Quota > Per User Quota". On the user level you can configure "Max File Size" in "Admin > Users > Edit user"
