Definitely don't stress, all babies are different and will only drink as much as they want, not what the formula tins or anyone else says they should be having.
At 3 months old, my DD#2 was having 6 X 120mL bottles a day and would have been lucky to have emptied each one of them, even now at 7 mths, she's only just starting to drink 180mL bottles.

As long as bub is happy, healthy and gaining weight there's not much to be worried about.