Authenticator code
What it is
The field behind the six boxes in the Confirm it's you pop-up. The pop-up appears before publishing to a home (and before some acts that cannot be undone).
What to enter
The 6-digit code shown now in the authenticator app on your phone. Only digits are kept; the sixth digit checks it by itself.
What it changes
A correct code lets the publish go ahead. You are asked once per sign-in (some acts ask every time). Nothing in the house changes. Nothing in the app changes.
If it goes wrong
A wrong code shows That code didn't match. Try again. After 3 wrong codes the pop-up closes and nothing is published. Codes change every few seconds; type the current one.