Most of the time, the "data-*" attributes follow a common pattern, signifying that the information contained in these attributes will be utilized by a JavaScript snippet. This holds true for the dynamicMedia component, where the data loaded under "data-config" is subsequently employed by the Scene7 scripts. If I am not mistaken, all the information is consolidated into this attribute from various sources, which is why you may need to set the config URL as well.
Hope this helps.
Esteban Bustamante