There are two ways to reset the trip part, which makes the car “forget” driving and battery behavior.
Reset “light” is through R-Link. This will reset the range indicator (GOM) to a value proportionally related to the capacity of the battery. In effect it forgets how (un)economical you have driven. It was used in the old days to check how healthy the battery was.
There is also a harder reset, called the “two pedal reset”. Keep the driver door open, start the car, keep the gear in N, press and hold both pedals and press up key on the windshield wiper control until the averages message appears in the display. Now hold that button. First it displays the current values, then it starts flashing, then the average values display —. Now let go. This reset seems to also make the battery computer (LBC) loose quite a bit of acquired parameters and the GOM shoots up to a crazy value.
The car will rather quickly re-learn the state of affairs. Just don’t rely on the range indicator on your first trip after a reset.