Keeping in mind that it's been years since I've even seen half these symbols, much less had to use them, I think he's doing a proof. K is apparently a superset of Ta + Va + Ya, and P intersects S.

What I really think is happening, given that he states it doesn't make sense after he's finished writing, is he's trying to do the differential in his hallucination and realizing that, because what he's written doesn't make sense (it's a mathematical proof instead of a listing of actual symptoms), he must be hallucinating.