can someone explain this lighting chart to me

i was under the impression that lumens dont multiply, 4x 2000 lumen bulbs dont equal 8000 lumens just better coverage right? so my question is, this chart says 5.3 125w cfl bulbs, is the same as 1 400w hps, but it says its the equivalent to 50k lumens, help please? heres the chart http://www.littlegreenhouse.com/guide3.shtml

Lumens do multiply, or add up.

ive read, on other parts of this site, that they dont, so whats the verdict

Here's a different way to look at it. If you had one plant, and one 125 watt Bulb.....You would get "X" amount of growth. Throw another 125 watt bulb.....under the same shade, and you will come close to getting double the growth. The reason here is not coverage as much, as it is more Lumen penatration. In this way the lumen do add, but the formula changes with distence so drastically, and coverage soon becomes the advantage. In the end, who cares what equals what....go for coverage with any bulb you use. It is sometimes more efficent to use lower wattages and more of them. Strive to use as little as possible with the greatest results.

Go outside at night with two flashlights. Point at the ground and Turn one on, then the second one. The ground will be brighter because the lumens are doubled. Or use physics - light is composed of photons - the more there are the brighter the light.

This is just another silly myth floating around grow circles. I think it comes from the fact that it is practically speaking impossible to get multiple cfl bulbs close enough to create a meaningful increase in light because cfl's are only effective within a couple of inches of the plant.

ight cool, so i think if thats the case, i might just use t5's imma try and grow dieselryder, dwc style