With ~3 million squares it would fit in a couple hundred megabytes at the very most, even without any compression. It may not be optimal, but it's certainly not unrealistic either.
3x3 is 510.1/9 - 56 trillion (and change).
> 196,936,994 m^2
Is equivalent to a perfect square with sides 14km long...they say it's a small world..but not that small.
https://solarsystem.nasa.gov/planets/earth/by-the-numbers/ Volume: 6.73 x 1011 cubic miles (1.083 x 1012 km3) Radius: 3,959 miles (6,371 km) Diameter: 7,918 miles (12,742 km) Surface Area: 1.97 x108 square miles (5.1 x 108 km2) Mass: 5.972 x 1024 kg
"m²" or "m ^ 2" universally refers to square meters (unless you've established unambiguously that you're talking about miles — and even if you have it should still be "sq mi").