This is the answer I got from Customer Care earlier:
"You can have multiple exits within a visit as in, during one visit I can leave your website multiple times and come back before the visit expires. All the exits will be counted, but when my visit expires- exited site will be shown as 1."
Which is not really convincing to me. I mean, why is session expiration handled differently here? And even if, why not just name it "session expiry" instead then?