Chuck - how old are you? Are you using a chart which looks at max heart rate, then uses % to determine fat burn, etc?
220 - 37 (age) = 183
183 - 65 (resting heart rate) = 118
118 * 65% (low end of heart rate) OR 85% (high end) = 76.7 OR 100.3
76.7 + 65 (resting heart rate) = 141 and 76.7 + 65 (rhr) = 151
The target heart rate zone for this person would be 141 to 151
You can also Google the Karvonen Formula - it is a bit more accurate... but is the same premise.
While this is the target heart rate for "fat burning" - you can also elevate your heart rate (85% to 95%) for short periods of time to burn more calories - research shows interval training can definitely help. In fact, that is a lot of the premise in the "Body for Life" workouts...
15 years as a Certified Athletic Trainer have filled my mind with too many options... and stuff is changing (i.e. the old 220-age for max rate, vs. Karvonen formula)...
Sorry for the long post.