Gauge chart - help with changing range to non zero start

[LB_]

I am trying to update a gauge chart that I made in excel to show a different range (50% to 100%)

The chart is currently done on a scale of 0% to 100% with the following input calculations:

Range
Start: 0%
Section 1: 97% (input value given)
Section 2: 3% (calculation is 100% minus 97% from above)
Total: 100%

Dial to show at 81%
Start: 145.8 (calculation is (81%/100%)*180 degrees)
Width of dial: 6
End: 208.7 (calculation is 360 degrees minus start value of 145.8 minus 81%)

This chart is working properly with this range but I am now trying to update the chart to show a range of 50% to 100% only. I can't seem to make this work though. Does anyone know how to do this?

I need to build multiple charts with the same scale of 50% to 100% so looking for the theory behind how to do this so I can implement again.

Thanks!