What is the MCN and the Disc Identifier?
Media Catalog Number (MCN) is the standard UPC/EAN product number, and should conform to the specifications of the UCC and EAN. See http://www.ean-int.org and http://www.uc-council.org for more information.
The MCN number must be 13 digits longs, but the UPC you were issued is 12 digits. The correct way to input the UPC code is to add a zero "0" to the beginning and it will show up correctly on the disc.
The Disc Identifier contains disc ID information, such as the catalog number and name of the record company, point of sale code, year of sales, etc. Each item shall be separated by a slash ("/").