@sanghun17 You can look at how the input scaling is used: PX4-SITL_gazebo/gazebo_mavlink_interface.cpp at 6b6f4749a74215b9a4fb81cfaa99a3950f13464d · PX4/PX4-SITL_gazebo · GitHub
The scale basically maps the normalized inputs [-1, …, +1] to something similar to the rotation speed values of the rotors, which gets consumed in the gazebo_motor_model. Therefore it should vary between models because the props have different thrust constants, and therefore spin at different RPMs.