If you're looking to view traffic specific to a particular Web Filter Category, you can do so in just a couple of clicks in the Reports viewer.
Select the report Web Filter > Top Categories (by request).
Next, click anywhere inside the pie slice for the Category you'd like to view.
This will pop up a prompt to add the appropriate condition. Click Yes to add it.
You'll see the condition appears at the top left-hand corner and any results will be filtered to just traffic matching that Category.
If you're looking for the numeric identifier for that Category (for use in an
is in condition or a custom Report), click the
Web Category (Web Filter) = <category> condition to see it.