Hi Ladyhawke,
Your method was the right one as this setting is used only for the manual focus. Just try the values and adjust them until they work right.
This is almost OK, except dividing by 9: The nine steps are distributed left/right around the best focus, so you have only 4 steps on each side to reach the 3-5 times HFR number. You should divide by 4. Anyway this is a very forgiving setting.
Regards,
Horia