not sure as I’ve got a 530 now and its different (better) than the 520. There has been some recent discussion that TrainerRoad workouts show “Step Average Power” on the moving needle of power screen. This is different versus Garmin Connect and TrainingPeaks workouts, which show “3sec Average Power” on the same screen. This is what I see on my 530 while using workouts from Garmin Connect and TrainingPeaks:
See how the top begins with “3s PWR …” - I believe with TrainerRoad workouts it starts with “Step Average Power”
More info here: