MH distance should i follow this?

http://img707.imageshack.us/img707/4411/1063932footcandlesmhdon.jpg

I saw this on someone elses post and was curious on if i should follow this? I have my light about 3-4 feet above my plants right now(Sunmaster Cool Blue 400watt) seems like it says 8 inchs is optimal but that just seems like it will be to hot, first grow so not alot of knowledge.

Easiest way to guarantee max light for your plants is to check canopy temp vs light height, and adjust accordingly. For the most part, that chart is pretty damn accurate.. but growing conditions or lack of fans would have a higher temp than you would otherwise, as an example.