How do unaccept and accept work? I see different reputation values:
Why do they differ?
The OP can change the accepted answer at any time. If he accepts your answer you gain 15 reputation points ("accept"), if he reconsiders after that you lose 15 points ("unaccept"). If the OP is indecisive and changes the accepted answer several times you get a high "accept" score but also a similarly high "unaccept" score (equal if your answer ended up not accepted or 15 lower if it was accepted in the end). In your screenshot the sequence for the first answer was:
accept -> unaccept -> accept +15 -15 +15
And even more fun for the second answer:
accept -> unaccept -> accept -> unaccept -> accept +15 -15 +15 -15 +15
In both cases your answer was accepted in the end and you ended up with a +15 net reputation change.