Power, not speed. Exactly because these kinds of kits don’t have a way to measure your power (effort), they need an external way to tell them how much you want

Power, not speed. Exactly because these kinds of kits don’t have a way to measure your power (effort), they need an external way to tell them how much you want them to be helping. So there are power levels (often 5) that change the power curve of the motor when it’s helping, usually helping more at lower speeds (likely uphill) and then fading out at higher speeds.