Probably a very newb question.
Is the default assumption that ammunition for every shot is tracked and each use of the Volley move consumes one shot with the exception of a 7-9 result where you may expend an extra one as well?
Similarly, when a Wizard (or similar class) casts a spell, he only loses a prepared spell if he rolls 7-9 and chooses that option. Otherwise he can cast the same spell next time if he or she chooses.
Just trying to get a few things sorted in my head.