The metadata of DUB is found in numerous documents, including audio videos, ebooks, and audio files. Data and image files could be part of them, however.
It is possible that the DUB number of files could mean two things. The first is adding sounds of any sort. Dubbing can also mean the addition of a second language to the film. Furthermore, it is possible to use DUB could be utilizaed to include background music, sound effects, and other sounds in a video that has already been edited.
The second meaning is derived from the source for the term Dub itself. It is derived from the English phrase double. Therefore it is possible that the DUB amount of data in your file could be a sign of a duplicated data stream, such as video or audio.