When they say that what they mean it is the equivelent to a 250 Incadesent Light bulb.
If you study the intensity of the red and blue spectrum of a HID you will find that although the HID r +B spectrums are only 10-20% of the actual light emmited the intensity of it far surpasses the intensity of any number of CFL, LEDS, or Flouros.
think of it like this.
a 1000 watt HPS outputs 150,000lumens directly 0" below the bulb
following the inverse square ratio of light law.
One foot below it is 75,000 lumens
and two feet below (recommended distance for a 1000 watter) 37,500 lumens
So you have 37,500 Lumens hitting the plant canopy of all the spectrums light.
So lets say that 10% of that light is Red and Blue, that means at that distance you have 3,750 lumens of JUST red and blue light, or at 20% 7500 lumens of R+B light.
If you do the calculations on CFL's which are allowed to pratically touch the plant
you start with (on the CFL you posted)
3600lumens
Now Cfls have at most 25% of thier spectrum emmitted R+B so
at 0 feet 25% of 3600lumens is 900lumens of R+B spectrum
So you are waging 900 R+B lumens vs. 3750-7500 lumens on a HID
and since Lights cannot combine into a bigger Intensity of light you cannot add another CFL to get to 1800 lumens of R+B.
Your entire CFL light fixture will be putting out a Max of 900 lumens as per this example.
Marijuana in its flowering phase Needs MAD MAX light, in fact If you calculate the R+B from the sun, a 1000 watt HID light doesnt even come close.
thats why Outdoor Indicas can be 6 feet tall and Produce as much as a 1 lb of bud, vs a indoor under a 1000 watter will not come close unless seriously vegged to twice the size of its outdoor counterparts.