iwlist Output
 

I am having difficulty understanding the output from iwlist.

It says "Quality" is xx/0 (xx is some number). The documentation I have seen has xx/100 or xx/94 or something other than zero. i understand that there is some relationship with signal-to-noise ratio.

If my Quality is 44/0 does that mean the signal to noise ratio is 44dbm?

I also have quite a few readings of 254/0 and 255/0. Are those erroneous values?