I have 2 reference books that list the shows in a different order and they are listed according to airdate.
The DVDs also number them but sometimes in different order.
My guess is that maybe the DVDs are arranged in production order, and they just aired them out of order the first time around ?
I'm not complaining, just curious - so far there are no continuity issues by having these "out of order."
Regardless, these are 2 very nice boxsets and I am enjoying them immensely !