Yes. Although I ran out of fingers and toes getting to 32. You can do any quantity using the ratio that is 5 parts (4 parts + 1 part = 5 parts).
So, if you only need 20 ounces of mixed paint, divide by 5 (20/5=4). Now multiply that by your ratio 4x4=16 oz paint, and 4x1=4 oz hardener, for a total of 20 oz mixed paint. This works much better if your gun cup is smaller than a mixed quart, or you only need that much to do a certain panel.
You can also use it just to verify your math, so here it is for your 32 oz and 8 hardener at 4:1 ratio:
I prefer using weight and a postal scale. Most manufacturers have alternative weight ratios, so I can mix any quantity I want right in the mixing cup with no measuring - just weighing as it goes in.