Why is that amazing? Also, you will never have 246 quadrillion blocks saved in your world's save folder.
The seed and algorithm determines what they are, so in a way they're already there. But yeah, you're not going to have the areas and each individual block saved.
I think they're just impressed with how big the world is.
While we're on the subject of larger than usual numbers, I find it kind of interesting that my computer has done over 4.48 quintillion (4,480,000,000,000,000,000) floating-point operations for BOINC so far in its spare time in the background. It's kind of relevant, because a lot of this was done while playing Minecraft and hosting a server for it.