No rhyme or reason, just pure luck. Over a LOOONNNNGGG period of time, you would have more or less reached your 85% payout. It's what is called "regression to the mean." A hihger payout means less for you in the long run. These gaming machines are a long term proposition, if you can't ride the short term, then this should probably not be your line of business. Casinos in general have so many machines, that it evens out in the short term. But yes, small operators will go ride the high volatility wave, especially those themes that have all kinds of multipliers. A less volatile title would probably be better for a small operator, slow earnings but steady. The titles with high volatility can generate a LOT of income fast, but it can also bleed you fast too, it's all in the numbers (or in this case the RNG).