If you mean Aboca Grintuss Pediatric (https://www.gdziepolek.pl/produkty/33889/aboca-grintuss-pediatric-syrop/apteki), then according to the manufacturer's recommendations:

- children under 6 years of age: 5 ml, 2-4 times a day

- children over 6 years of age: 10 ml, 2–4 times a day

In practice, this means that until the son is 6 years old (i.e. until his birthday in September), a dose of 5 ml should be used. After the age of 6, the dose can be increased to 10 ml.

The manufacturer does not provide for increasing the dosage depending on the child's weight.

I attach helpful materials: https://www.gdziepolek.pl/kategorie/kaszel-u-dziecka

Syrop grintus