You should use the chartsJS module. Do your math to calculate percentage, then create a pie chart with two data sets. The first will be your percent done and the second would be your percent remaining.
Or you could use the progress circle widget.
I'll second the progress circle widget. It takes those 2 attributes you describe to create the circle: a current value and the max value (goal)
In the app store here: https://appstore.home.mendix.com/link/app/47783/Mendix/Progress-circle
Or you could use: