A lot of the foods in our database that only have serving sizes are entries from other members. If it's a recipe, as long as you know the total number of servings the recipe makes, then you can do the math to figure out the nutritional info per serving. Calorie counting is never an exact science, but that should give you a good ballpark estimate.
Hope that helps,
"You may have a fresh start any moment you choose, for this thing that we call "failure" is not the falling down but the staying down." Mary Pickford