the way I thought automatic works (please help me out here Mike) is whatever gear you're in at whatever [sensed] speed, you (more the computer automatically) shift down only 1 gear (usually like 3rd) unless you come to a complete stop or brake down to like, say, >5MPH.. If you do reach >5MPH or stop, the car then shifts down to 2nd to 1st. If you only slow down say from 45 to 15 for a turn, you should only be downshifting a gear; unless you have manually done so (which wouldn't be suggestable)
Another thing, the car will usually downshift to 3rd. That means (sorry for not mentioning it earlier, I'm no expert) if you were able to go from say 60MPH to about 1MPH given the alloted road'age with no braking, no gas, then it won't downshift anymore (the auto goes through 2nd rather quickly) until you completely stop..