I believe the idea is that a developer creates a game (that has a house edge). MP basically licenses that game and uses it's house bankroll to bankroll it. In exchange, MP, the investors in MP, and the creator of the game all split the profit that is generated from the house edge.
In the example given, RHavar forgot to make the bet have a house edge, so the math works out negative for the investor.
That's right, I reworked the example where the numbers this time should add up. The issue was only affecting the example, not the code (which does these calculations properly). Thanks for pointing out the mistake, btw )