I remember now. You press the set button for 3 seconds to enter the normal setup. A short press avances it to the next parameter. Wheel size is easy because it goes in real sizes like 26". One of the settings is 0 or 6km, which is how the throttle works. 6km gives you only 6km/h from it.
While you're in setup mode, you press and hold the SET button for 1o seconds to go to the next setup mode where there's two more parameters. One of them is the max speed.
The plus and minus buttons increase/decrease any of the parameters.