@franz, thanks for getting back so quickly. (Are you ever not working??) I'm glad you already know about this, but it would be nice if someday in the future it either didn't go back to the defaults, or it somehow said that it was going to reset to the defaults. I really puzzled for a while why changing the soil type all of a sudden wanted to add 52 minutes to the watering time! I finally caught the MAD defaulting.
In my case, I have a newly planted and redone perennial zone. Since it's brand new and it's been really hot here, I'm starting out with the root zone being less than normal, and then gradually I'm going to get it down to what it should be. I'll just have to remember to go back in and reset the MAD whenever I make a change.