Maximum is 2 teaspoons per quart depending on how soft you want it.
1/2 teaspoon per quart works for us, you can get it out of the freezer and stick a spoon in it without heating it up or anything. It’ll stay in a cone upside down.
2 teaspoons per quart made it soft enough that if you put extra scoops on a cone, they’d slide off after a few minutes.