3 Sword Style floating text is showing +1/0 or +0/1 for each empty slot when it gains stats, instead of the 3/0,0/3.  It appears it is actually gaining the correct amount, just displaying the bonus wrong.  Also the astronaut line sorta makes the final assassin irrelevant, the assassin kills 1 unit and dies, where as the astronauts effectively remove a unit and gets a ton of stats that you didn't have to invest anything in.