See attached photo of two SAS and two Norwegian boarding passes. Notice that they both have a class field with two letters - one big and fat to the left and another a little smaller to the right.

As far as I know (on SAS at least), it's the smaller one to the right that is used in the milage calculation. But I'm not sure if this is the same with Norwegian?

I'd would be awesome if someone here knew more about this

Bonus: If someone could explain a few of the more exotic fields like "Notes" and "Sequence" as well, it would be cool