I am working with a linear, static finite element model with C3D10, S3 and S4 elements. The shell and solid elements refer to shell sections and solid sections respectively. The materials referenced within each shell and solid section have a defined mass density. My model also has nonstructural masses assigned to element sets (defined via mass per unit area). 

My question is as follows; when I run the model, the .dat file reports mass information. My .dat file states, "TOTAL MASS OF MODEL 2.125085". However, when I open the .odb in Abaqus/Viewer, and go to Query Information -> Mass Properties -> All Elements, a different mass is written to the message window. The message window states, "Mass properties for Whole model....Mass: 1.85702e+00". These two mass values are 0.268065 kg different. 

Why is the .dat file total mass value different from the queried total mass in the odb?