Iam having the TSW 1000... that has 150 watt------- And i let my seedlings grow on 100 percent in a distance of 75 cm ( its a2x2 tent)
mabe we can aadpt this Numbers to your 300 w Light
you see it how they grow,,,, and its way better to start low, than burning them early-----
If they are stretching to much, go closer// give more Wattage, if they are dwarfing under the Light.......and building short internodes give more Distance// dimm the Light
here on Gd is a representant of Mars Hydro... you may ask her
i let you the link