no he means run a 150 CFM fan for intake and a 250 CFM fan for exaust. the ducting size is perfect at 6" for a 4x8 space.
i run 1 1000 watt light per 6x6 space, or 2x 600 watts for 4x8. the 2x 600 watt lights will give you a better light distribution without sacrificing light penetration. they also let you put them closer to the plants, its not sacrificing anything, it actualy improves the room considering the space. since the lights are air cooled they can be placed 6" from the top of plants.
the absolute maximization of space would be plants spaced at 2 plants/Square foot in a hydro perpetual SOG. clones taken and veged for 1 week in a second room, then moved to the flowering room and flowered when they are small. you could fit 60~ plants on hydro tables, harvesting 6 plants every week (9-10 week strains) or 7 plants every week (8 week strains). average 12-20 grams per plant, thats 60+ grams per week....
flood tables on separate reservoirs that way you can change the nutes per week to give the best results. use 4" rockwool cubes and cram the plants in. you can harvest ALOT in a short period of time.... it turns it into a full time job