Perhaps it is a simple mistake where someone signed on the wrong line. In Tennessee we have to sign our names on the registration rolls.
That would be extremely doubtful if the man was there four minutes after the polls opened. That would require someone to have signed on his line within those four minutes and the poll watcher is supposed to check that the man signs on the right line.
A legitimate mistake here in TN should be easy to spot. The name in most cases would be different, and would match the printed name on the line below or above where they should have signed.