Measuring CDs in “Megabytes” is actually crap!
A CD which is labeled as “700 MB” contains 360.000 sectors. Overburning is, depeding on the media, usually possible up to 367.000. The most I achieved once on a Taiyo Yuden media was 371.000.
If you burn normal data CDs (“Mode 1”), a sector can store 2048 bytes of your data. Then, 360.000 sectors are 737.280.000 bytes, which is about 702 MB. In Mode 1, your burner will add 276 bytes of C3-error correction data.
If you burn “Mode 2 Form 1”, then you can still only store 2048 bytes of user data per sector, but the burning software must calculate the C3-or correction data. Therefore, burning unreadable sectors is possible (in simply writing crap error correction data).
If you burn “Mode 2 Form 2”, no C3-error correction data is stored, so there is more space for your files. One sector can then store 2324 bytes of user data, so 360.000 sectors can then store 836.640.000 bytes, which is 798 MB.
If you burn RAW, which is only done for audio and “raw images”, one sector can store 2352 bytes, so 360.000 sectors can then contain 846.720.000 bytes, which is 807 MB. Burning of plain data files in RAW mode is not possible, it would result in an unreadable disc.
If you have a clonecd image, then there will be additionally 96 bytes per sectors subchannel data for each sector, which is additional 96*360.000 = 34.560.000 bytes, i.e. 33 MB.
That’s why a full clonecd image of a “700 MB”-disc is 840 MBs large.
The burner will add more error correction data later, so that one sector contains 3232 bytes later, but current burners do not allow to interfere into this process in any way, so “RAW”-burning and subchannel writing (“RAW-DAO-96”) with 2352+96 bytes/sector is the “best” mode.