This is a snide comment used in the northern hemisphere towards boys known as major horndogs 6-8 grade. The true meaning is unknown, it is a chance for girls to drive boys crazy, no male knows what it means, so it is either a turn on, or intense insult.
(Boy tells a girl he likes her. Next night has a naughty conversation through text with her bestfriend about bubblebaths. Friend of course fesses up to the first girl.)
Girl: 1590 shitface.
Boy: huh? WHAT?