Ok thanks i have the same size tent and put the 2 lights to 24 inches.
Id guess the 1 unit would be fine for 6 babys bro . I have 1 unit above a 1.2m tent thats getting pretty full View attachment 285833& there all bushy girls ...the babys are prob 40" away & only stretching a tiny bit.
You can go to 24" like Nam said no worries with a GN ,but 20" would be to close imo... plus @30" you will get a nice spread over 6 plants.:group:heres the GN section of the forum ...https://www.autoflower.org/f109/.