[ColinWright]

You have misunderstood, or misremembered.

You don't take "3" from the first, you consider three, but choose something that's not "3", so the number you are constructing differs from that first number.

Then in the second place you don't take "5", you choose something that's not "5", so the number you are constructing differs from that second number.

And so on. So every time you have a list of real numbers, it cannot contain all real numbers ... you can always construct many, many, many numbers that are not in your list.

But I'm not sure how this is related to what we've been talking about. If you understand what I've said here and are still confused, maybe you can be a bit more specific. If you have not understood what I have said here, perhaps you can ask more specific questions.