In https://support.trainerroad.com/hc/en-us/articles/4404665021595-Progression-Levels#:~:text=Progression%20Levels%20are%20determined%20by,successfully%20they%20completed%20these%20workouts. it says that
As you complete rides, Adaptive Training analyzes and adjusts these levels based on the relative difficulty of your workouts in each zone, as well as how successful you were in completing them.
How is your “how successful you were in completing them” determined? Is it based on heart rate? Your answer to the survey score?