Selecting distinct/non distinct from same data set

Hello. In a call center environment, each call that comes in is placed into an appropriate category. Calls are placed by participants.

The goal is to count how many times the same participant called into the same category within a 15 day period. Those records need to be tabulated, other calcs remain, but this is the hard part.

See attached file for 2 queries. Only difference is that one is distinct, the other is not selecting distinct. If I could somehow subtract the counts from eachother i would get at the needed number. But because it has to be summed as a group with participant, I'm not sure how these could be subtracted. Maybe a sub-select query of some sort?

Thanks for any advice.