example, a 3 minute mp3 is about 3MB, a 3 minute song in regular format is about 30MB, so if you burn mp3 files onto a CD then you'll get app. 10times more music on a 80min cd than normal. But as I said before, you need to burn a mp3 Project or a Data CD. When creating an audio CD your mp3 files will be converted back and you just have the regular limit for audio CDs.
80min = 700MB of data, 700mb = app. 20 songs in wave format
700MB = app. 200mp3 = app. 600 minutes music.