I've run across this issue myself and from what I understand DP's or "Density Pixels" are a virtual unit of measurement used by Google for their Android platform who size varies according to the resolution of the screen you are designing for, similar to "points" for Apple devices. There are online calculators that can do the conversion for you between DPs and pixels.
Here are a couple of resources I found for you:
How to design with density pixels in Photoshop?
General Google search on DP vs PX