What does it mean "Enter a 5 digit signature ID"?

[KaseyG]

Your 5 digit signature ID on the Consent to Disclosure screen (also called a Self-Select PIN) is how you sign your federal return if you're e-filing. It's the electronic equivalent of manually signing a paper return.

If the field is blank, just enter any 5-digit number. Same goes for your spouse if you're filing jointly.

And if you see a prefilled 5-digit number in this field, you can either leave it alone or re-enter a number you like better. It really doesn't matter.