I can lift a 200 pound piece of glass with a tiny vacuum sucker. It's the atmosphere keeping that thing up there, and the 2" of ground clearance is what you see around the edge, we don't actually know what the distance is where the evacuation happens. For all you know it as a 3' x 7' plate underneath it that floats just above the surface.

I've done a lot of vacuum picking and it is surprising how large an object you can pick up with a tiny bit of surface.