kbps stands for kilo-bits-per-second.
Standard CD quality is 44.1 kHz at 16 bits, so that equals 705,600 bits per second or 705 kbps, about double the precision or quality of 320kbps.
But don't forget that you have 2 tracks, so that equals 1,411,200 bits per second of a CD quality stereo mix, so that is possibly 4 times more information or quality compared to 320 kbs.
Not sure how they account for stereo or not stereo with respect to kbps information (?)
Although, when I use Real Player to convert CD audio files into data files, they are listed as 1,411 kb WAV files. So maybe that is the answer, and 128kbps is roughly 1/10 of CD quality at 1,411 kbps.