yea its not anout how many plants. with my 400, i was able to pull a qp really regardless how many plants i grew, one plant = 4-5 ounces when i vegged for 3 months. 4 autos gave me 4.5 ounces. and i once did 6 autos and got 4 ounces. i think its all dependant of your light and size/quality of the environment.