It is normal if you fill it over the cup the 6th bar will show up, but will go away within 5 to ten miles. The 4th bar last the longest and when mine 1st bar starts blinking I still have a little over a gallon left. The gas gauge is retarded!
When the last bar starts blinking, it doesn't mean that you are about to run out of fuel... I've often ridden another 40 miles after the last bar started to blink before refueling, which still leaves about a half gallon of fuel remaining in the tank. The fuel gauge was intentionally designed this way, to ensure that there is enough fuel remaining in the bottom of the tank to keep the fuel pump submerged and within its operating temp.
The fuel gauge isn't "retarded"... it works just as it was designed to. No one would want a fuel gauge that starts blinking 10 or 20 miles before the tank runs dry, would they?
Then, this is the problem. Never indicates that you are full. Always missing 1 bar, even ending supply of and seeing that this stuffy gasoline. After fueling, I wait 1 minute, with the bike vertical but does not appear the last bar. In some hypotheses appears.
I don't understand these parts of your post.
To see the sixth bar on the fuel gauge you need to fill the tank completely, with fuel over the top of the baffle plate. I fill my bike to within a half inch of the top of the gas cap flange. Even then the sixth bar only lasts about 20 miles before it disappears.
It seems that a lot of new motorcycle owners fail to consider that the fuel tank is egg shaped, and therefore the fuel gauge is not going to be linear. In other words, the fifth and sixth bars on the fuel gauge represent the relatively small volume of fuel at the top of the tank. If the tank were a square or rectangular shape, the gauge readout would be linear and consistent as the fuel is used.