Just a quick chart on the difference from what you set your fla movie fps to what the actual fps is when played back on the mac flash 5 player.

set fps vs. actual fps

fps set to 16-20 reads out -> 15fps
fps set to 21-30 reads out -> 20 fps
fps set to 31 reads out -> 30 fps
fps set to 59+ reads out -> 60 fps