When they say 700MB on a CDR they mean 700 Logical MB (1MB= 220)
So 713 Million Bytes falls below 734,003,200 Bytes which is what the theorectical amount is. But minus about 18,000,000 for TOC and Session mgmt... you got your magic number of ~716 Million Bytes or 682.8 MegaBytes
800MB/90Min CDR's actually hold 838,860,800 Bytes or then again - 18.2million bytes for TOC and session mgmt = 782.5 MegaBytes.
800MB/90Min CDRs Are [link|http://www.aec-media.com/cdrsil16x90m.html|available (100PK)] right now. I would stick to 80Min/700MB CDRs (which I am sure Yendor Mike meant!!!) as they are easier to get.