People are confused by the fuel gauge. Plus the fact that some of them where not calibrated properly lead to a lot of confusion.
First of all the fuel gauge only works for the second half of the tank. This is explained in the manual. For the first 10 liters the fuel gauge will show full and the range indicators will display a range with a plus sign, the range being the distance you will do on the half tank. For the second half of the tank each bar is approximately two liters.
If this is not confusing enough, there is also a special behavior of the fuel gauge, caused by the split tank design. The fuel gauge is mounted in the right side tank bottom. When the bike is parked, on the side stand, the fuel will will run to the left side fuel tank trough the connection tubing on the bottom. With little fuel (1/4 and less) in the tank most fuel will end up on the left side. When you start riding, the fuel gauge will indicate a very low fuel level, blinking red. After a few minutes the fuel will moved over to the right hand side again and balance out, then the fuel gauge will show normal level again and the fuel range will increase to what it actually is.
In short, don’t trust the fuel level as you start the bike. Ride for three or four minutes to get an accurate reading.
This is not a defect, but a normal behavior of the tank design with two low halves. If KTM had mounted the fuel gauge in the left side, it would show a much too large level when you start riding, which might leave you stranded shortly after. One option would be two fuel sensors, one on each side and some software to clear things up, but hey, more complexity, more money 🙂