Yep it's always advised that there's some left in the bottle. If they continuously drain bottles thats when it's advised to go up an Oz x
Yes! I have a 9 week old and does anything between 2-4 ounce each feed. It is annoying that you have to waste formula but as time goes on you can work out when they will take more, for example taking more in the morning than the afternoon etc.
Yes this is normal! You want them to be leaving a little bit so you know they've had enough, and if they start emptying the bottle the majority of the time, then that's your sign to go up to the next amount 😊