Istituto Espresso Italiano defines a specific Certified Italian Cappuccino using 25 millilitres of espresso and 100 millilitres of steamed milk. This gives you a named recipe to understand when comparing café drinks.
For the version on your own menu, record the espresso, milk, foam and finished cup size. Compare that written build with an instant mix as two different preparation options, rather than assuming the product name gives you the same ingredients or quantities.