Instead of using the max level, try adjusting the settings until you find the maximum comfortable suction level for you instead. This means the highest level where you can pump without experiencing pain or discomfort, which encourages the best milk expression.
For reference, your Philips Avent electric breast pump can be set to a max level of 16 on the motor unit, which is equal to -350/-360 mbar (-262/-270 mmHg).
