[sinsinwar]

How does checkMesh differentiates between tetrahedra, and 4-faced polyhedra (or between hexahedra & 6-faced polyhedra)? I understand that the two are exactly the same, geometrically. But how is checkMesh able to segregate them? Is it due to different face orientations?
For example, I ran checkMesh on a mesh with 426104 cells, which had the following distribution:

Overall number of cells of each type:
    hexahedra:     333362
    prisms:        16704
    wedges:        0
    pyramids:      0
    tet wedges:    976
    tetrahedra:    3
    polyhedra:     75059
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            4   3902
            5   6098
            6   21701
            7   1313
            8   644
            9   26821
           10   212
           11   209
           12   10024
           13   46
           14   71
           15   3349
           16   4
           17   12
           18   650
           21   3

Does this mean that the total number of tetrahedra is 3+3902 = 3905, and the total number of hexahedra = 333362+21701 = 355063?