You want to understand how agent channel filters work in relation to agent policies.
Release : 15.x
Component : Agent configuration, agent policies
The order of filtering of agent data is:
Anything filtered at step 1 is not available for evaluation in step 2
A complicating factor is the behaviour of True Type files on the agent configuration channel filters, which will recognize certain file types by a single signature. For example all Open Office type documents are seen as a single type. Thus filtering on .docx at the agent configuration level will also filter on .pptx, .xlsx etc. More details on True Type files here. At the policy level however, these file types can be distinguished.