When taking a priority assignment, the game states that Fate reward will be 11, but, when you have finished the level - you only get awarded 8 Fate.  This has happened 100% of any of the missions I've taken with this format, when I've checked my Fate counter on the bridge - I have only received 8.

I've also noticed this happens on worlds where you just take a random mission - still says 11 Fate and you only get 8 Fate.