What drug are you giving him? It's usually ok to round up, but the drug and why does factor into dosing.
The PP is incorrect. It would be 1 &1/2 pills per day, not 3. Often the dosing per day is divided equally, if possible. In that case you'd cut them into quarters and dole them out (3/4 each dose, twice daily). What does your vet want you to do?