The profit is generated from a price action within the grid. The profit per grid is a % price spacing between adjacent grids, minus % trading fee for both grids. The trading fee is always included in the spacing between grids to make sure that a bot will not trade in negative.
Now let's have a more deep look into how the profit per grid is calculated. Let's assume that the spacing between two adjacent orders is 0.5% and the exchange's one-side trading fee is 0.1% then profit per grid is 0.3%.
And here is why: To complete one buy and one sell orders we would need to pay our exchange 2 transaction fees for filled orders. This fee is included in pre-calculation, and then the spacing adjusted accordingly to cover the exchange's fees and generate income.
Please note that the exchange's commission is automatically remembered for your account after the first trade you make on Bitsgap.