What does the reservation confirmation say the reward code is?
If you do "view receipt" it should show something like this:
OnePass Miles Debited/
Reward Used:
150,000/CS6M-DG6
That should hep you figure out how they decided what to charge you. Or just call back and ask why it is being charged as an 8 instead of an 8B since you think KE is supposed to be 8B.