Well, I reckon this is the wrong behavour, and so calling it a bug.
The count node should go negative if decremented from 0.
If the above is argued against, then if I set the initial value to a high value then it should drop below that value on decrement.
Yes, sorry, I was confised after all .. it was a long day.
I knew about the daisy chained windows descriptions, the confisuion arose because I had started with an old composition with the old properties.
Sorry for wasting your time.