The Code Record Type designates the ad as an original or a derivative of another related ad. Original is the default value and is most often the appropriate selection. A derivative ad may be a revision of an original ad. When Derivative is selected, you can enter the Ad-ID of a Parent record it is associated to and select a derivative type. Here is an example:

An ad is created with code ABCD8957363. Three new versions of the ad are created with the last 3 seconds of the ad including different offers. The three versions are marked as:

Code Record Type: Derivative
Parent Record: ABCD8957363
Derivative Type: Revision

See Ad-ID Field Descriptions for descriptions of the various fields in the Ad-ID system.