What is the size of the largest set of 10-digit phone numbers such that no two numbers in the set are different by only one digit?

Question

The problem asks for the largest set of 10-digit numbers which are more different than just by one digit. For example, the set canNOT contain both

$1234567890$

and

$1234527890$

as they have only one different digit.

I've been stuck on this problem for a little while as I can't seem to find any way to approach it.