I think what might make sense then (seeing some Account Data for certain passengers) would be that the data is pulled from the E-ticket in the passengers reservation if you have one, as the "Class" portion on the last 4 flown segments given credit for that we can see will usually say "K" or some discounted fare class if you've flown it, and if you've upgraded it would mark along the likes of "KF", as in original class of service paid for then class of service that you sat in. You would receive the credit for the first letter of the two only then.

That's just my logical two cents, I could be way off. But it makes sense

Happy Travels!
Kai

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Any opinions expressed by myself are mine alone and may not necessarily reflect the opinions of my employer, SkyWest Airlines, or those of our majors partners, United Airlines, Delta Air Lines, and Continental Airlines, respectively.