Newborn

Hi Everyone! I've just started formula feeding with made up formula today and I'm wondering once you add the formula to the boiling water and it makes it slightly more because of the volume would you then class the extra as what they've actually had? So for example if I make up 60ml and then add the formula it turns it to 70ml so if he takes all of that does that mean he's taken 60 or 70ml? Thanks!