The documents and material located on the Cisco Web site can help solidify complex topics. More details appear at http://www.cisco.com/en/US/products/sw/secursw/ps5052/index.html.
For more information on tuning sensor configurations, go to http://www.cisco.com/en/US/products/sw/cscowork/ps3990/products_user_guide_chapter09186a0080157f9f.html.