Mass Properties, Moment of Inertia, units of "kilograms*square millimetres" ?

My Document Properties Units are millimetres for length and kilograms for mass.

The Mass Properties dialog reports Moment of Inertia seemingly in units of kilograms*square millimetres.

What I rember from school is that moment of inertia is area in mm^2 x distance in mm x distance in mm.

Kilograms don't come into it, and the units should be mm^4.

How should I interpret the numbers in this report?

SolidworksAssemblies