That’s correct the X axis is the left throttle and the Y axis is the right throttle. Launch game go to setup, controllers, advanced, flight control,
Throttle axis: drop down menu select X axis x-55 throttle then
Right engine throttle axis: drop down menu select Y axis X-55 throttle.
When you move the throttles separately you’ll see the blue slider move and they are working correctly. For the F-16 it doesn’t matter if you set the right throttle but this way when you fly a two engine aircraft you’ll have control of each engine.