I think that chart is off a bit.(looking at 1000 watt coverage only - optimal is 4X4 and can go 8X8 not 10X10)
The 400 should be just fine as already stated by ^^ posters.
in12 ft2 you are looking moreso like this..
Minimum Lighting 25 watts Per Square FootLighting
The minimum recommended lighting for your area is
300 watts
Ventilation
The minimum flow rating of your fan should be
70.0 Cubic Feet per Minute (CFM)
Power Requirements
This setup will require
3.3 amps to be available at all times for safest operation*
Optimum Lighting 40 watts Per Square Foot
Lighting
The optimum reccomended lighting for your area is
480 watts
Ventilation
For optimum ventilation the flow rating of your fan should be around
77.0 Cubic Feet per Minute
Power Requirements
This setup will require
5.2 amps to be available at all times for safest operation*
Maximum Lighting 60 watts Per Square Foot
Lighting
The maximum reccomended lighting for your area is
720 watts
Ventilation
Going this way you will require a fan with a flow rating of at least
91.0 Cubic Feet per Minute
Power Requirements
This setup will require
7.8 amps to be available at all times for safest operation*
Additional Comments
Getting to these points and or over it is highly reccomended the grower use Co2 in their room as your plants will only be able to photosythesise a certain amount of light before needing a Co2 boost to benifit