It is a green washing gimmick. I had it on previous Renaults too. Serves no purpose whatsoever, and the sole principal is to make you think you are being a careful and green driver. The only displays that have any relevance to your driving style are the bar that moves across the screen and denotes what your current MPG is, and then the numerical display of current MPG. The only thing I take notice of is the average MPG over all the mileage I have done. When I bought the car, I zeroed the B mileometer, and have never reset it. In nearly 15k it tells me that I have averaged 70MPG.
To hell with the cabbages.