So you can check and adjust some functions of the board computer.
Normally, you don´t have to cut the fuse. To get into the adjustment mode: Turn ignition off. Push the "reset" button at the bc- lever and keep it pushed. Turn ignition on. Release the "reset" button: Now you are in the adjustment mode.
You can select your area (EU, Canada, USA, Saudi Arabia, Japan, GB), display some different indications and you also can tune the consumption indicator, as it doesn´t display proper values.