Class Service?
 

I am reading alaska airlines mile, it says:

Economy Class Cabin:
Earn 70% of actual flight miles* flown in Q and T classes of service.
Earn actual flight miles* flown in Y, W, B, M, H, E or K classes of service.

What does this mean? How do I find out if my "service" is which class?

Your Korean Air e-ticket will show 'Booking Class' along with other information for each segment of your ticket. It will also show 'Fare Basis', the first letter of which will also indicate the booking class. If you do not yet have an e-ticket, but are somewhere in the purchasing process, you should see a link to 'fare basis' following the flight details. Again, the first letter of the 3 or 4 letter code will indicate the booking class.

Fare Basis Code
TLW3MUS3

So is it T class then?

I'm not quite sure what you mean by "service" class, but what you quoted is simply the earning rates for the different types of fares. As for the actual in-cabin experience, it's all the same. The FA isn't going to treat you differently because you're on a Y ticket as opposed to a Q ticket.

correct!, sorry if I confused you with the possible length of the code, the ones I had been looking at were shorter.