I think the problem lays with the fact that 699MB is a rounded number and you still have to have a TOC (table of contents) hidden on the disk... On MP3's the TOC is usually larger because there is more information to store so if the TOC is 600kB and the actual size is 699,450kB it will not be big enough to store. Also there are small tolerances on disks where you have around ±100kB available on the capacity (as I said, 699MB to write and 700MB available are usually rounded off figures)