It was outlined in the manual to an extent, but basically, most parking positions have multiple stopping positions to accommodate the various different types of airplanes that could park there. The general idea of said positions is to park the airplane in a manner such that the jetway would be more or less in the same general area when connecting to the door of any airplane of any size. Otherwise, if you went with the nose gear being on one line (there isn't a way to have multiple nose gear stopping positions), the jetway might connect to the door on one airplane fine, but might not reach the door of a different airplane because the door is in a different position relative to the nose gear. Hopefully that made sense.