You already know it but here is a reminder.
BB Hard or Extreme levels are a waste of time and fuel as they screw you out of SM.
Normal you get 10,350 + 400 SM = 10,750
I have verified this amount of SM is achieved for Normal Level.
Hard claims 15,500 + 600 =16,100
BUT you ONLY get 11,850 this includes the 600 loot
so you get a whole 1,100 more for doing hard level
Loose more fuel in doing so and the MIX boxes are the same crap as Normal level.
Not worth it.