When you set up a position, you are creating an intention to swap one token for the other. Then, some external user can come and execute the swap for you, honoring the desired frequency of course. When they execute your swap, you are charged a 0.6% fee on the amount that was swapped. This fee is then split between Mean Finance and the swapper. Since you don’t have to execute the swap by yourself, you don’t need to pay any gas.