Is it normal if my 4 week old eats 100 ml (3,5oz) formula every 3 hours?

My 4 week old son has had very severe colic-like symptoms, so his pedi suggested we try out lactose free formula. It seems to work, his tummy doesnt seem to hurt as much anymore, but on the box of the formula, it says that 1-2 week olds should eat 100 ml (3,5oz) every 4 hours, about 6 times a day, and 3-4 week olds should eat 130 ml (4,5 oz) 5 times a day. But my baby eats 3,5 oz (100 ml) every 3 hours. Just when he was breastfed. I'm worried about overfeeding him. Is it normal, or should he eat less?