Leveraged Position

Exercise on total return on leveraged investment. Why do you add the comission per share to the initial investment then substract it from the proceeds? I believe it is not counted finally, because either they pay it at the beginning or they deduct it from the proceeds.
If 13500+24=13524 is the initial investment and 27000-9000-360+600=18816 is the final proceeds, the return is (18240-13524)/13524 equal 34.87% or (18216-13500)/13500 equal 34.93%