I, myself, am just blown away by this grow, being under COBs and using the full Roots Organics dry nutrients line and 707 medium. Like, I didn't really know what to expect.
Highest lumen (or PAR) per watt for that particular product. In our lighting usage, it means the most electrically efficient at converting electricity into light. This directly translates to higher efficacy overall.
This is specific for that manufacture/product/light/chip/diode. Top bin is specific to manufacture (Ex: Cree) and a specific product (Ex: CXB3590), and even further broken down for each spectrum in most cases.