[PvK]

I'd estimate between 100 Km and 100,000 Km, but as others have said, it is a very abstract representation. Unless it is an inertialess 2-D universe, for instance, the squares would represent distance in three dimensions, as well as velocity, etc.

Note that in the real universe, the Earth is roughly 12,750 Km in diameter, and the distance to the moon is about 384,000 Km. This is partly why I gave those figures above.

PvK