It didn't exactly take much homework or effort. Like 5 mins reading on light Intensity and a $20 Meter. It's a good way to save electricity and heat.
It's sound advice. I don't see the issue. If grade five math terrifies you, feel free to keep going on your way as it also works.
I found out I could save a lot of heat and electricity and still get the same results. When I was going by arbitrary numbers such as distance and percentage, I didn't realise my dli was 65+, and that was the cause of my heat and stress issues.
Some people spend hundreds on hydro setups, nutes and environmental control for fun, I buy a $20 Meter instead and stick with potting mix, cheap tents, slow release ferts and tap water..