I'm using the word "dish" to include everything the "dish" washer is expected to clean.
So we have a plate, possibly a bowl, one or two utensils, and a cup at each setting - so between 3 and 5 per place. Then we dirty another 10-20 dishes preparing and serving the food, so that adds about 1-2 dishes per person on average, so between 4-7 items to be washed per person, per sit-down meal.