Galley allows you to specify how much of each component’s nutritional values are in the finished recipe. This allows you to account for an ingredient or component not being fully absorbed during recipe's preparation (e.g. a marinade might only contribute 10% of its nutritional values to the final recipe).
To edit this value, go into the "Nutrition" tab of a recipe. Then, scroll down to the "Component Nutritional Values" section and edit "Contribution %".