You should consult with your pediatrition before you change your baby's quantity of formula. Baby's come in all sizes and your baby is more than likely eating just what they need to stay healthy and grow.
I used to give 5 spoons of formula milk in five ounces of water which would make it around six ounce of milk. Babies should not be overfed as they can have a tummy pain or upset or just uneasiness. Overfeeding also makes a child very lethargic. We all like to see plump babies but overfeeding is not the answer.
Yes you can over feed a baby, at seven months old your baby should be eating five to six times a day and taking in eight ounces at a time. At this time your baby should not be waking in the night to eat or drink and you should have started him on solids.