If it anything like my set up on my yamaha the trim sender unit has a small arm which rests against a type of bracket which is fixed to the bar the engine tilts from, these brackets have a tendancy to break or shift position, sometimes if you tilt the engine all the way up the arm of the sender unit can 'go over' the bracket stop which it moves against.
In your case if its showing two bars I expect the bracket things may have shifted slightly.
Get really close to the outboard and locate the bracket thing the sender unit moves against and check its position, there is one screw undo the screw slightly and move its position (rotate the bracket slightly) trial and error and you should get it in a better position and re tighten.
They are a pain, ive replaced one sender unit and one bracket in past 6 years and had to re position the bracket twice (usually after work was done on my outboard and hydralics) cos if your not careful the bracket can move.
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