I'm not entirely sure what you're asking, but the supplemental heating source will operate to meet any remaining heating load that isn't met by the heat pump.

For example, for periods with cold temperatures, the heat pump has reduced capacity and may not meet the entire heating load. So the supplemental heating source will operate to try to meet this remaining load. For periods with moderate temperature where the heat pump has enough capacity to meet the load, the supplemental heating source will not operate. You should be able to see this behavior by looking at the hourly outputs in DView.