Yeah normal! Just like us adults, some days we are gluttons, some days we are on a diet and some days we are just too darn lazy to keep up with how many meals we’ve eaten. As long as your baby is pooping and peeing as per normal, no vomiting, it shouldn’t be a cause for concern. My baby used to drink 120ml at one go but sometimes she drinks half of it and it worries me like mad. But she has normal number of diaper changes and is as happy as she has always been. After a while the milk intake will decrease once they start solid food.