I had that same question when I was in the beginning with my little girl.  It is hard to explain the difference but from what I can tell you is that when my little girl is on good treatment she still has chubby CHEEKS with a definite chin and defined angles on her face but with CHEEKS.  When she is oversuppressed her whole face becomes very round and to be honest she has more of the "jowl" look than the cheeks.  Her chin is not as defined etc.  It’s really hard to explain and I know it doesn’t help right now but when I look back at her pictures it is so OBVIOUS to me now exactly when they were up-ping hermedication -

Good luck hope I was of some helP!