900 AP Transmitter Output Power

What should this be set to? From what I can see the highest we are allowed to put it is at 28 dBm. Is this what access points should always be set at so they are transmitting at the most powerfull setting? Or should they be higher/lower?

See:
http://motorola.canopywireless.com/supp … light=eirp

and

http://motorola.canopywireless.com/supp … php?t=1762