Game points (class/vehicle points which result in your GAME score) are actually given a x2 value. You'll notice that say, your progress in a class will be DOUBLE what you got with that class that round.
Reward points, are given a double-dipping in the additional points.
So for ex:
You get 1,000 Assault Points, 1,000 Tank Points, and 1,000 Reward Points.
It shows: 2,000 Assault + 2,000 Tank + 1,000 Reward + 1,000 Additional = 6,000!