I did some off roading with my Jeep group.
When we aired down, I zeroed the fuel consumption measurement.
We stayed in a nearby motel overnight and in the morning I checked the fuel consumption.
It reads 20.4 litres per 100k
That's your MPG or in your case, l/100Km. When you reset it, it shows a very high number, like when you're coasting or braking. Reset it and then take off from a light , it will show a very low number, then rise as you get up to speed into a higher gear. HTH
It's your current MPG. The gauge tops off at 99 MPG.
You really are getting 99+ MPG at that moment if, for example, you let your foot off the gas and coast down a hill. Unfortunately you can't do that forever and you'll see when you go up a steep hill you'll drop to 2-3 MPG. It all averages out to a more reasonable MPG number.
That gauge is really helpful in figuring out exactly what kind of driving gets what kind of MPG. In a Jeep it's not exactly intuitive. For example there is a major MPG difference between doing 80 MPH on an empty highway compared to using ACC and planting yourself behind a truck doing 65. Doing 80 on an open highway actually gets worse MPG than doing 25 MPH in 4WD on a bumpy rutted trail.