Hi e1 and sorry my bad english

I collect some so called facts about globe earth, and then I made some calculations.

First so called facts about globe (ball) earth (I use "km")
Radius(ball) 6 378 km
Diameter(ball) 12 756 km
Circumference(ball)  40 000 km
Area/acreage (ball) 507 000 000 square kilometer

Then calculations (flat earth ie. circle) assuming, that distance from north pole to the edge (south pole) ie. radius is 20 000 km (same distance as in surface of globe earth):
Radius (circle) 20 000 km
Diameter (circle) 40 000 km
Circumference (circle) 126 000 km
Area/acreage (circle) 1 260 000 000 square kilometer

So what do you think about those calculations? Acreage of flat earth is 2,5 times bigger than globe earth assuming that my calculations are correct (ie. radius of flat earth) and that makes me thinking about the look of the real map of flat earth. Or have I  missed something in my calculation or made some mistake?

Problem is, how to present surface of a ball (3d) in 2d level circle (paper or screen) and vice versa. You cannot do it without adding data or removing data (ie. water/land) if you want to keep the "picture/map" uniform/united. Has anyone thought this before?