Codec Bitrates?

I have posted before asking about recording mp3's, but have decided to record wma's using the wmencoder. The question I have now is about the codec bitrates. In order to encode, a profile has to be set for the Source Group. I displayed a list of the Profile Names in the profile collection, and it is as follows:

Windows Media Video 8 for Color Pocket PCs (225 Kbps)
Windows Media Video 8 for Color Pocket PCs (150 Kbps)
Windows Media Video 8 for Dial-up Modems or Single-channel ISDN (28.8 to 56 Kbps
)
Windows Media Video 8 for LAN, Cable Modem, or xDSL (100 to 768 Kbps)
Windows Media Video 8 for Dial-up Modems or LAN (28.8 to 100 Kbps)
Windows Media Video 8 for Dial-up Modems (28.8 Kbps)
Windows Media Video 8 for Dial-up Modems (56 Kbps)
Windows Media Video 8 for Local Area Network (100 Kbps)
Windows Media Video 8 for Local Area Network (256 Kbps)
Windows Media Video 8 for Local Area Network (384 Kbps)
Windows Media Video 8 for Local Area Network (768 Kbps)
Windows Media Video 8 for Broadband (NTSC, 700 Kbps)
Windows Media Video 8 for Broadband (NTSC, 1400 Kbps)
Windows Media Video 8 for Broadband (PAL, 384 Kbps)
Windows Media Video 8 for Broadband (PAL, 700 Kbps)
Windows Media Audio 8 for Dial-up Modem (Mono, 28.8 Kbps)
Windows Media Audio 8 for Dial-up Modem (FM Radio Stereo, 28.8 Kbps)
Windows Media Audio 8 for Dial-up Modem (32 Kbps)
Windows Media Audio 8 for Dial-up Modem (Near CD quality, 48 Kbps)
Windows Media Audio 8 for Dial-up Modem (CD quality, 64 Kbps)
Windows Media Audio 8 for ISDN (Better than CD quality, 96 Kbps)
Windows Media Audio 8 for ISDN (Better than CD quality, 128 Kbps)
Windows Media Video 8 for Dial-up Modem (No audio, 28.8 Kbps)
Windows Media Video 8 for Dial-up Modem (No audio, 56 Kbps)
Windows Media 8 Fair Quality based VBR for Broadband
Windows Media 8 High Quality based VBR for Broadband.
Windows Media 8 Best Quality based VBR for Broadband.
Screen Video High (CBR)
Screen Video/Audio High (CBR)
Screen Video (CBR)
Screen Video/Audio
Screen Video Medium (CBR)
Screen Video/Audio Medium (CBR)

When I set the Profile to Audio for Dial-Up(Mono, 28.8), the resulting file has a bitrate of 20kbps. I am wanting to encode to a smaller bitrate to create a smaller file. any ideas on how to edit the bitrate??????????????

Thanks,
Kendal

20 kb/s is a pretty horrible bitrate already. if you encode any lower than that, it's going to sound like a bowl of rice krispies. you have to have somewhere to store the audio data...

All this is going to be used for is recording transcription in the medical field. Not for music. I am trying to keep the file sizes down because some of the transcriptions can last up to 15 minutes long.