They are just saying “but what if we replace the set of integers with a larger set”. I think they are also defining this larger set in a base 10 specific way.

They are just saying “but what if we replace the set of integers with a larger set”. I think they are also defining this larger set in a base 10 specific way. I think they basically mean the 10-adic numbers, which, unlike the p-adics for p a prime number, uh, I forget exactly what goes wrong, but I suspect it has like, zero divisors or something like that.