Average calendar day at AA means we'll get 5:15 x number of days per trip. You could therefore have a 7 hour day on day one, 2 hour day on day two, 2 hr on day three, and another 7 hour day on day four and get paid 21 hrs. The trip just has to average 5:15/day.
With min calendar day, the minimum per day is 5 hrs and 15 min. So in the above example, you'd get paid 7 hrs on day 1, 5:15 days 2 and 3, and 7 hrs on day four. Min is much better than average (SWA and FDX have this figured out).
The end result will be longer pairings (more 4 days and 5 days), less commutable trips, and more flying (the optimizer will make it more efficient). BUT, you should work fewer days per month for the same credit. Won't affect our reserves at all, except that they'll hit 73/76 hours sooner. Also requires more manning.
Both are obviously better than our 1/1 (1 leg, sit 30 hours, 1 leg home) that only pays 11 hrs for three days, but it'll involve more work.