rapture envelope question

hey everybody!  
can anybody explain to me how sync envelope in rapture is supposed to work??? 
let's say i have an amp envelope that looks vaguely like this... /\  if i set the amp eg sync to 1 i'd expect that if i hold a note for a bar the eg would cycle once during that bar. if i held the note for 2 beats it would get to the top of the curve and if i triggered another 2 beat note immediately following the envelope would restart.
this isn't how it works in my experience and i've had a bit of trouble figuring out how exactly it DOES work...
any help or comments???
THANKS!