trouble burning 80MB mp3's to 700 MB CD-R

I’ve been trying to burn lectures from a class that I’ve been recording on a Digital Voice Recorder. They start out as .rec files, the software for the DVR converts them to wav. files - I’ve been using Media Monkey t o try and compress them further as MP3’s. Anyway - The file range in size at the end of all of this from 80-120 MB. But they’re listed as just over two hours in length. I haven’t been able to burn them to CD-R’s even though they’re smaller than the 700 MB limit, supposedly. (I’ve tried burning the not-so-compressed wav files also, which should also be under 700 MB, with no luck).

Any suggestions?

Thanks!