THR Target Heart Rate

98 55% 
107 60%
116 65%

...Calculating your THR is 220 minus your age. We're supposed to keep our rate at 55% when we first start out, then move to 60%, then to 65% once we're in condition.

So you take your answer (220 - age) and multiply it by 55%, 60% and 65%.
You'll find it's almost impossible to get the rate to stay at exactly the number you want (I went nuts trying to do that!) so I keep it within one or two points of the THR in either direction...

I have chased mine within 10 points but I try to keep it as close as possible. I hope that helps!