Leif
Adventurer
I read the rules to be as Nightbreeze said.  When you inflict a multiple of damage (usually just double) you roll the dice multiple times.  You never roll once and multiply.  That means that a roll of twice maximum damage for one crit is EXTREMELY improbable.  (Happens one time out of sixty-four crits for a longsword, or other d8 weapon.  And since a crit probably only happens about one time out of 100 attacks, we're talking about a 1 in 6400 probability, if I recall my math properly, which is by no means EVER certain!)