Need help reconciling quantities in this recipe

Here's a recipe from a package of chocolate chips (edited, but not substantively):

2¼ cups all-purpose flour
1 teaspoon salt
1 teaspoon baking soda
1 cup brown sugar, firmly packed
½ cup granulated sugar
1 cup softened butter or margarine
1 teaspoon vanilla extract
2 eggs
1 package [=12 ounces] chocolate chips
1 cup chopped nuts, optional

Preheat…. Combine…. Add…. Drop mixture by rounded teaspoonfuls onto non-greased cookie sheets. Bake 8 to 10 minutes. Recipe yields approximately 2 dozen cookies.

Now, I figure we can't count powdery ingredients like flour as adding their full volume to the batter: they get condensed when wet. But the liquid ingredients should add their full volume: specifically, the cup of butter should account for a cup of batter. The cup of brown sugar is firmly packed (and it's pretty moist, too), so I figure it should account for another cup of batter, or very nearly. Finally, all the other ingredients — including 2¼ cups of flour, two eggs, and a lot of chocolate — surely add at least another cup to the batter. So we've got at least three cups of batter.

The yield is about two dozen cookies, so each cookie is made of:
(at least 3 cups of batter) ÷ (about two dozen) = (at least one fluid ounce of batter).

Yet the recipe calls for the cookies to be made of "rounded teaspoonfuls", surely not fluid ounces. (A fluid ounce is six (flat) teaspoonfuls.)

Where did I go wrong in my reasoning? (Or is there simply a mistake in the recipe as printed?)