A 99-minute, 4.7-inch (12 cm) CD-R can hold as much as 999.3 megabytes of data. The 99-minute CD-Rs blanks, however, are not as popular as the standard 74-minute, 670-MB disc because of recording and reading issues associated with the former.
Although different CD-Rs are marketed with a stated maximum data storage capacity, one can usually write more, or "overburn" data into the disc beyond the stated capacity. This is because the data storage capacity of CD-Rs are measured by the Red Book standard audio data that makes an allotment for at 90 seconds of digital silence.
The silent or blank area is called a "lead out" and this is included in most CD-Rs along with other standard areas, such as the lead-in and the program area. This same blank area may be utilized to write additional data into the disc in one CD burning session.
Multi-session disc on the other hand loses available data storage space with each data burning session. On the first burning session, approximately 23 megabytes of data is lost. Subsequent data burning sessions will result in the loss of 14 megabytes of storage space each session.
Some CD-R drives also use special techniques in order to write more data into the CD-R. However, the data written into the CD-R may not be compatible and readable in other standard CD-R players.