On a large scale, what this means is that the fund can look for large ups and downs because they gain every time there's an up, but they don't lose when there's a down.

Now if you parallelize this (so it's happening at the same time with many different customers), it means they can focus on risky bets. Maybe half their customers will win and half will lose, but the fund makes money on the winners and isn't hurt by the losers.