A friend adjusted mine for me...it's now dead on. Full is full....empty IS empty.
Used to sit above full for 200+km's before moving. It'd hit 1/2 and then drop quickly.
Now...I checked it at different levels of filling and it couldn't be closer.
I can send you my two tunes if you like and you can compare them and work out what he did. May or may not be different to what you have to do.