The confirmation map is the part of an address answer that says, for each of five parts, which dataset stood behind it: the postcode, the street, the house number, the town and the region each get a source name, unconfirmed, or null.
What Spaw answers
confirmation is an object with the keys postal_code, street, house_number, locality and administrative_area. A value names the dataset that confirmed the part: postcode_directory (the national postcode directory lists it), postcode_area (the town is one the directory lists elsewhere in the postcode's area rather than under the code itself, or, where the postcode's region is a single city such as Mexico City, that region's own name), register (a national address register followed the address that far), range (the house number sits inside a range the register publishes for the street), company_register (an open company register lists companies at exactly that building), mail_drop_list (a mailbox operator or a registered agent publishes the address), and pattern (the postcode only matched the country's shape). unconfirmed means a dataset that could have confirmed the part did not; null means nothing could check it at all.
What it is not
unconfirmed is not wrong. A partial register that does not carry a street has not said the street is missing, and the map reports exactly that: not confirmed, by a dataset that might have. The verdicts live elsewhere — exists for the building, locality_matches_postcode and administrative_area_matches_postcode for the town and the region — and the map is the evidence beside them.