well you have roughly 16 square feet to work with. You could start and finish all 10 ladies if you wanted. I am guessing that the 400 watter only puts out around 50,000 lumens. 3125 lumens per square foot. Little low but will work.

to answer your question. You could plant 1 plant per square foot or 1 plant per square meter. depdning on how you want to grow. if these aren't fem seeds then i would do all ten because fall out rate is what around 50% or so. personally i would grow all 10. i like the 1 plant per square foot. always workd well for me.

or to be safe only do 5 at a time. but all 10 would fit just fine.