I think that means that Fox only ordered that many episodes. That's why they made one that didn't air, the network ordered that number of episodes, but networks very frequently cancel shows before airing the full order. Sometimes they air the remainder in the normal timeslot, other times they just don't air them, frequently replacing the show with a rerun of a well-performing show. I can't remember the show, but I seem to remember one that got cancelled and the network ran a marathon of the remaining episodes, just to get them out of the way.

As far as I know, I haven't heard of a network cancelling a show before the order was out, and I doubt that a show like Fringe wouldn't at least get the remaining episodes aired, if not only released on disc.