Motion detection levels

[braindead0]

I'm playing around with the demo app and wondering what the motion levels reported in the event mrean. Using the demo app when motion is detected there's a grid showing numbers for 'motion' in the various cells. These number seem to vary a lot, I believe I'd seen them as high as in the 20's. Is this an expression of how much movement, velocity... or what.

And does it have any relation to the motiongrid values (I think not, but maybe?)