true wattage

Hi this sound stupid but if my mars hydro is 600w but the true watts used is 100 is that gona mean that if Im able to get 1g/w its gona be based on the true watts?? (100g)

I have a 24x24x36 grow tent and I want to put 4 plants in it and use a led light grow it, but I'm not 100% sure what wattage led I should use, alot of the Web sites I have looked at said to use around 143 watts but they also said theres a difference on what the web site will say vs. The actual...