The app's meter just shows the input level, while the red light on the H9 shows the effect overloading. Depending on the effect and the frequencies involved, it is possible to overload the effect without overloading the input. So, the red light on the H9 is the main thing.

But, you are unlikely to damage the H9, and if you don't hear any unpleasant distortion, don't worry.The sound is the thing.