Fun fact: a 10 billion kiloton nuke detonated in New York city would be enough to cause 3rd-degree burns to everyone in the Northern Hemisphere.
And if you replace all those digits with a 9 you do the same to the entire world except the part on the opposite side. For yours, there's probably enough energy to alter the rotation, and
maybe even alter the orbit of the Earth. I actually think that at that point you're starting to confuse the program. I went up slowly and it started wrapping around the world, and I got bigger and the blast radius shrunk.
EDIT: try 999,999,999,999, and compare it to the same with one more 9.