What does T/X mean on class of service paid? I just flew JFK-LAX today and was #2 on the upgrade list with no more seats available. I asked the gate agent if there were any no-shows but he said no and told me to board.

I noticed that all my past flights in which I received an upgrade are listed as T/X on the account history but the ones I did not just have a single fare letter.

Does this mean they upgraded someone after me on the list because I already boarded?