+10$ means you ran ten dollars below expectation. So you should have only lost 21.6 buyins.
Quote:
Also wondering is the $EV diff only calculated for AI hands and thus the hands that actually make the showdown would not be covered by this stat?
Yes. Also if you get 95% of the money in on the flop as a massive favourite, then villain hits his two outer on the turn and the remaining 5% of the money goes in, this will show you getting all of the money in bad. All in EV is also only one form of luck, there are others which can't be so easily measured, like how frequently you cooler your opponents when you have the nuts.