Rule of thumb: 100 calories per kg per day for babies. So if your baby is 20kg, he would need around 1000 cal.
Now, the meals follow the 5:5:3:2 rule. 5 portions of starches, 5 portions of veggies and fruits, 3 portions of dairy, and 2 portions of proteins (3 if you are vegetarian) per day.
So if your kiddo has 4 meals, it should be balanced across these. Don’t overdo milk as that might kill his appetite for other foods!