Your menu plan is made up of a mixture of 'meals' which serve 1 or 'recipes' which serve more than 1 (usually 2/4).
The menu plans have been designed for one, so when assigned a recipe, the program will assume you make the whole serving (i.e. for 4) and will distribute the left-overs throughout the week. If you plan to cook for more than 1, you should use the 'meal swap' option to swap out any 'Leftover' meals to a new recipe.
If you are cooking for more than 1, the shopping list will take into account the number of serves in a recipe. I.e. if you are cooking for 4 people, and you are assigned a recipe that serves 4 people, the ingredients for that recipe will remain the same in your shopping list. If you select to serve more than the serves in the recipe (i.e. recipe serves 4 but you choose to cook for 5), the ingredients for that 4-serving recipe will double to ensure there is enough for 5 but there will be leftovers.
If you find, calculating the shopping list is too difficult with the involvement of recipes, use the 'meal swap' option to swap for a meal (only serves 1). When you calculate the shopping list to cook for more, the ingredients will just multiply as expected.
If you have further questions, please feel free to contact support and we will be happy to assist.