http://en.wikipedia.org/wiki/List_of...umiya_episodes
That should explain the numbering. Originally, the episodes aired out of chronological order based on the novels. I watched it according to the airing schedule the first time, then rewatched it in chronological order and honestly preferred it according to the first airing schedule.
Chronological (season 1 only)
2, 3, 5, 10, 13, 14, 4, 7, 6, 8, 1, 12, 11, 9
Things get even funnier with season 2. I suggest looking up the 2009 airing schedule and follow that if you want to do things chronologically.
XI Wiki


