Air Delay for Max Range

I need to know how interpret the Air Delay in the Wireless Manager. Why some SM have in green the value andothers in red?  Is something to be worried or is just informative?

The AP is colocated alone (not CMM or any other AP and is charinng the spectrum with Wimax Radio in a channel of 20 MHz and 3412.500 GHz. 

I think it's just to bring your attention to the fact that you have a client about 14 miles out... (and another about 11 miles)  Depending on the frequency band, the environment, and AP settings that may or may not be a good idea...  Based on the signal level indicated in your screenshot, it looks like they're doing great.  (assuming no/minimal interference)