The +10 is because the 10% fee does not apply to your original $100, only to profits. So if you would have $250 without the fee, rather than 250 * 0.9 = $225, you end up with $235.
The +10 is because the 10% fee does not apply to your original $100, only to profits. So if you would have $250 without the fee, rather than 250 * 0.9 = $225, you end up with $235.