Roughly 200 teaspoons per quart
Roughly 50 teaspoons per cup
On average ... a full size Large Fowl laying hen eats 1/4 pound of feed per day ...
Roughly a pound of feed is about 3 cups ... so roughly 150 teaspoons per day of commercial feed.
150 teaspoons X 10% = 15 teaspoons per day of "non-scienctific nutritionally balanced commercial feed" ... or "treats"
One quart (200 tsp) ÷ 15 tsp (per bird) = will provide 13.3 birds with their 10% "treat allowance"
Edit to add ... looks like aart beat me to it ... while I was figuring ...