combination feeding - how much formula to give?

[alexx2]

We have just started introducing a bottle of formula for my 16 week DS. He feeds 5 times during the day, then has a dream feed about 22:30 and will usually feed twice in the night. We've started giving him a bottle of formula at 17:30ish, then I BF after his bath and we're just about to make the dream feed a bottle too.
My question is how much formula per feed? At the moment we're giving him the recommended 190ml/6 scoops of aptimil hungry baby formula but he only takes about 5-10 mins to guzzle this and always finishes the bottle. When breast feeding he can nurse for 20-40 mins. Is this just because the bottle teat is easier/more efficient for him to feed from and he's not looking for the comfort of a breast feed, or should we try giving him a bit more formula each feed to ensure he's full up?
TIA

My FF 16 week old DS takes 6 ounce bottles at a time if that helps.

This is a tough one as you have to weigh up giving enough milk to satisfy the baby while not too much so it impacts on your supply (presuming you want to continue mix feeding). We introduced one bottle a day about this age and the lactation consultant said to give 80-120ml of formula. I continued breastfeeding until 9 months but we gradually increased the amount of formula in the one bottle so at the end it was 210ml.