How GSA SER checks that backlink is indexed?

How GSA SER checks that backlink is indexed?

I want to check if my backlink indexed manually.

I've tried to search for site:domain in google but in result didn't find my backlink but GSA SER shows this link as verified.

it's "info:<url>"

Thank you Sven for answer but when I check with this all my verified links are non-indexed. Why then SER shows them as verified?

Never mind. I just mixed up verified with indexed

That column is called "Indexable" and means that this link can be found be search engines. It does not mean that it is indexed.