Chapter 15 Unified Threat Management for FortiOS 5.0 : Web filter : FortiGuard Web Filtering Service : Configuring FortiGuard Web Filter usage quotas : Quota hierarchy
  
Quota hierarchy
You can apply quotas to categories and category groups. Only one quota per user can be active at any one time. The one used depends on how you configure the FortiGuard Web Filter.
When a user visits a URL, the FortiGate unit queries the FortiGuard servers for the category of the URL. From highest to lowest, the relative priority of the quotas are:
1. Category
2. Category group