How can I reduce Chart Area without resizing Plot Area of a graph?

HI
After AndyPope's excellent explanations I add:

Try enlarging the plot area to the maximum size of the Graph area.
Then adjust (reduce) the Scale of the graph width to where you need it.
In your case, after resizing the plot area, reduce the Graph Width Scale percentage to 67 and see if that's what you're trying to achieve.

Attached is what I did with your graph.
HI,
Mario