All newborns respond differently. If your baby is having mother's feed also then the quantity will be less through bottle feed. At the end of the day if your baby is active. Passing urine 5-6 times a day and weight gain as per age it is ok.
Next Steps
Observe the activity of the child and see whether the baby is passing urine 5-6 times a day and keep a check on the weight gain
Health Tips
Breast feeding is the best. The baby should be on exclusive breast feed till 6 months no other milk to be given. Till 6 months water is also not needed