I don't have mine connected right now, but out if the top of my head, you need to set values for 0%, 25%, 50%, 75% and 100%.
The gauge could work at values 0, 10,20,35,50 aswell as 800,1300, 1650, 1788, 2134 or even reverse, so starting at 0% with a higher number, going down.
Just sweeping the slider towards something that shows a value isn't enough. obviously at the lower values, a change of 1 or 2 could have a huge impact on how the gauge responds. But same holds true for the higher values...
I just start to find something at 50% and work 'around' that, so to 25% and 75%...