mass won't change enven though I change the material

Hi guys,

Strange things happen to me. Mo mater how I assign the different material, but mass property report always tell me the same mass as steel density. from Mass Properties-> options I can see the density has been changed to the assigned material. but from the report, it still gives me the same density and the same mass.

How can I get the right mass?

SolidworksParts And Features