Incorrect description. It should be similar to "CActiveRecord::onBeforeFind()", like following:

This event is raised before an AR finder performs a count call.
If you want to access or modify the query criteria used for the
count call, you can use {@link getDbCriteria()} to customize it based on your needs.
When modifying criteria in beforeCount you have to make sure you are using the right
table alias which is different on normal count and relational call.
You can use {@link getTableAlias()} to get the alias used for the upcoming count call.