A MAPR asset assigns surfaces to certain parts of the JSP mesh, allowing material effects and surface effects (such as out of bounds) on the level model.
The asset data starts with the asset ID, then an int which defines the amount of entries in the MAPR table, then the entries themselves. Each entry has the following format:
||Surface to be applied
||Unknown - this is likely an index into the JSP to choose which mesh the effect will be applied to.