You can also go to apple-> system preferences -> keyboard. Click on the keyboard tab and check the box that says "Use all F1, F2, etc. keys as standard function keys.
I actually did 63 - 91 herblore about 1-2 months ago. I kept track and it costed about 76m. I did mostly Ranging Potions. I think 1000 potions took me about 1.5hrs but can't remember well.