The meta information of DUB can be found in many different files, including audio, video and e-book files. Images and data files can be among them as well though.
The DUB value of the files can mean two different things. First, adding sounds of some kind. Dubbing is also known as providing another language version to a movie. In addition, a DUB can be used to add background music, sound effects, and other noises to an already edited video.
The second meaning comes from the origin of the word Dub itself. It comes from the English word double. Thus, the DUB value of your file can also indicate a duplicate data stream, like audio or video.