CO2 required for full power usage?

So I’m researching grow lights and while looking at the HLG Scorpion Diablo the specs page has a total output of 2130 PPF and says “CO2 required for full power use”. Someone explain that please. Thanks!!

YouTube videos can explain better than me. LSS OVERKILL and CO not needed unless experienced or commercial growing. The light is my Xmas pressent, I hope. The SD light would be good in my 4x 4 tent, but $1500 for more grow? Maybe good, but I need to get the cure to work.
Dr Bruce Bugbee is great