You want to know the meaning of DENIED, OBSERVED, and PROXIED as it relates to the access log field sc-filter-result.
OBSERVED
Indicates that at some point, policy invoked a category lookup, ie, a "category=" trigger was evaluated.
DENIED
Indicates that the request was not served. Typically this means the user received some form of an exception.
PROXIED
The category was not a factor in the policy decision. Examples of this: The policy used to process the request did not include a category definition, such as source:any, destination:any, action:allow.