If you would like to repeat a meal and add leftovers in the meal plan, simply add the recipe to the day and meal where you would like to have leftovers. Then choose Add as Leftovers. The extra servings you need will automatically be added to the original recipe.
If you choose Add as a New Recipe, the extra servings are not added to the original recipe.
For example, if I were preparing Slow Cooker Honey Soy Chicken on Sunday, I would want to use leftovers for lunch on Monday without having to cook again, so I would choose Add as Leftovers.
However, if I was making the Microwave Cinnamon Pear Oatmeal on both Monday and Wednesday, I would likely Add as a New Recipe, since I would want to prepare it from scratch since it is such a quick recipe that tastes better freshly made.