OK. That's enough. We have to guess that it's not a KT controller because it's a King Meter display rather than a KT one.
I'm going to have to make a lot of assumptions, but maybe this is what you're experiencing:
There's mainly two types of power control systems: Current control, where each level on the display causes the controller to give an exact fixed amount of power, like level 1 is 60w, level 2 100w, etc; speed control, where each level causes the controller to give you enough power to reach a fix speed, lie level 1 gives 8 mph, level 2 gives10 mph, etc.
Yours is probably speed control. The power algorithm is something like this: From zero speed, give maximum power until the speed is 5 mph below the level's target speed, then decrease it gradually until it's zero at the target speed. This is very similar to a cruise control in a car.
Let's say that you were on level 3 with a target speed of 12 mph, pedalling along at 12 mph. You'd be pedalling without any help from the motor. When you encounter a hill, you start to slow down, so the controller starts to increase the power from the motor in an attempt to get back to the target speed, but that's not enough, so you continue to slow down until you get to 7 mph or below, where the controller gives maximum power. The only difference in the levels is the speed at which you can get maximum power.
