You're correct. My Season 1 DVD included a episode out of sequence.

@WardenclyffeTower said:

All these sources say there are 12:

http://www.tvguide.com/tvshows/king-of-the-hill/episodes-season-1/100241/
http://www.imdb.com/title/tt0118375/episodes?season=1
http://thetvdb.com/?tab=season&seriesid=73903&seasonid=6633&lid=7
http://www.tvrage.com/King_of_the_Hill/episode_list/1
https://en.wikipedia.org/wiki/List_of_King_of_the_Hill_episodes#Season_1:_1997
http://kingofthehill.wikia.com/wiki/Season_1

I got Episode#13 on my HDD it have duration 22m15s. Have a look please: EPISODE#13

@WardenclyffeTower said:

The archived listing on Fox's website is the production order instead of aired order. The episodes are listed primarily by aired order on this website. You can create an episode group for the production order.

As it turned out there was no problem, because URL that I gave have mess, Season#1 have episode from Season#2(Episode#9 "The Company Man"). May be closed. Thank you!