Something is seriously wrong here...
Below cube is 1m^3, density of 1000 kg/m^3, so its mass is 1000 kg (or 1E3kg in E-notation). The surface area is correct, design summary too.
If I edit the root assembly, and inspect Physical Properties, I get a mass of 2E9 kg. It should be 2 x 1E3 kg = 2E3 kg. So it is 1E6 times 'heavier' (more mass really) than it should be. Out by a factor of a million. Design summary, volume, surface and CoM is correct. I didn't check mass and inertia moments.
I'll submit a ticket, this cannot be.