An Ad-ID code is 11 characters such as ABCD1234000. Codes are 12 characters only for high definition (HD) or 3D video codes, in which case an H or D is added to the end (ABCD1234000H, ABCD1234000D).
Prefix: The first 4 characters of a code are the prefix.
Code: 7 characters that follow the prefix. There are various format options that determine how these characters will be generated.
Definition: The 12th character is only used for HD and 3D videos.