Does it do that when you're riding?
I'm not at home now so can't check mine, but is that a 'live' l/km reading, which tells you what your consumption is as you are riding? It will change as you speed up, slow down and change gear.
In which case, it isn't an average, and if you check it when the bike is not moving (as it is in your photo) it will not be correct.
To be honest, these things aren't very accurate anyway. I keep tabs on fuel consumption by resettng the trip meter when I fill up, and dividing distance by litres when I fill up. That gives a true figure, and it never agrees with what the on board computer says.