Talking about the A320. TLA means the physical position of the thrust lever.
The lever is connected via rods to the throttle control artificial feel unit which basically is a friction brake and provides the notches for the different thrust lever detents.
Thereafter the motion is linked to the throttle control unit that contains the resolver and potentiometers and sends the signal = TRA to the ECU and flight control system.
The relationship between the throttle lever angle and throttle resolver
angle (TRA) is linear and : 1 deg. TLA = 1.9 TRA.
So TLA and TRA are linked values measured at different places.
Hope I could help you...
, I just realized your Q might be related to the 737, but maybe you get the clue anyway.