UPC/EAN Extension 2 is used to encode information (such as issue number) for newspapers, books, and other periodicals.
2-digit supplement can be used to track which issue of the magazine is being sold for sales analysis or restocking purposes.
Since the 2-digit supplement is mostly used in conjunction with a UPC-A, UPC-E, EAN-13, or EAN-8 barcode, it makes the barcode longer and requires wider scanners. The use of the extension is limited to publication industry.
Encoding both 2-digit extension and 5-digit extensions follows the same underlying structure. A left-hand guard bars, encoded as 1011 followed by two to five data characters, each separated by a separator character, encoded as 01. There is no "stop" character. The barcode is assumed to end when a character separator (01) doesn't follow a valid character.
The 2-digit extension is not always the same as the "Issue Number" that is printed on the cover of books and publications. Sometimes the encoded issue number just gets incremented with each issue. In other cases, the encoded issue number may just be the number of the month of the year, or the week number, depending on the frequency with which the periodical is published.
One can use Label Flow™ barcode software for printing UPC Extension 2 publication labels..