Zero.
Never put wax paper in a microwave. It burns up and smokes and stinks horribly and makes you cough and gives you a headache for the rest of the day.
I forgot that there was wax paper in the KFC biscuit box and I put it in the microwave to heat up the biscuits. It was absolutely horrible. >_< *holds throbbing head* So now I'm hoping that this headache I've had all afternoon will go away with some sleep.