That's because Andy in the past asked whether we wanted to keep the Japanese km/ltr consumption figure or converted into Australian's favourite ltr/100 km figure. It seemed to be a consensus that majority want the 'Australian' way of ltr/100km.
Earlier, there seems to be no objections for the programmer to convert it into ltr/100km, so if the Russian programmer do go ahead with that conversion, the higher the number is the least economical, so the base of the leaf is green and the tip above is red (least economical) as you will consume more fuel / 100km travelled. so the Russian programmer is on the right track.
If you don't like the way it is, then it's probably too late now as the screen looks like will be converted to ltr/100km as part of the english conversion.
IMHO, the Japanese way is better because by travelling economically you can see the whole leaf turns green.
While converting it into the Australian way, you will end up with a leaf with a green base but colourless tip.
too late to go back now, I reckon since Andy said the conversion is finished and they're only working on distribution scheme/anti piracy methods.