When two recipes share an ingredient and one is removed from the cart, the credits may not change. This happens because the remaining recipe contains an ingredient with enough serving sizes for more than one recipe. Some commonly shared ingredients are sauces, cheese, sandwich bread, and tortillas.
When adding a new recipe that includes an ingredient already present in another recipe, the credits for the shared ingredient are not added to the total credits again. This is because the shared ingredient is already accounted for in the credits of the previously added recipe.
When editing your deliveries, remember that credits for shared ingredients are only counted once. Removing a recipe won't give you back credits for shared items if they are still required for other recipes in your cart.