I would use the lowest setting on the seedlings and use the maximum distance recommended by the manufacturer. With out using a PAR meter to know how intense the lights are your just guessing and risk burning them. As the plants grow you can slowly lower your lights a few inches at a time especially if they look like they are reaching for the like by stretching too much. Typically maximum light is used during mid to late bloom then the last 3 weeks before harvest lower the light intensity. I would keep an eye out for signs of light stress in the leaves like the leaf blades curl up or they look like they are folding up like a canoe. Also the leaves closest to the light will begin to get pale in color. Hope this helps.
