maybe its expected result was -25K but he finished +5K
Yes, it's something like that. The extra 30k (or whatever - it's hard to put accurate numbers on it because he constantly switched accounts and so it was hard to know which accounts were him) is the amount nakowa should have lost but didn't.
To make a cleaner example / thought experiment:
If someone comes to the site, deposits 10k BTC, bets it over and over again, making a total of 3 million BTC wagered, and ends up breaking even, the expected profit increases by 30k BTC, but the actual profit doesn't change. The shortfall increases by 30k. Where is the missing 30k? The player doesn't have it - he only deposited 10k BTC and withdrew 10k BTC. The site doesn't have it. It's merely a shortfall of expectation, I guess.