I am not sure how the reefkeeper controller I have does it but for the heater port it only gives you an on temperature. There is not a high setting. The tank temp is always, 24 hours a day 78.4 - 78.6. The only time it goes out of the range is if I manually turn on the frag tank lights while the display tank lights are on. I have seen in that case it go to 80 and the fan kick on.
Think of it like this Josh. The heater itself has its own built in thermostat. It is likely that it is cycling on and off with tolerance less then .5 degrees. We could test that, fill a bucket with water, stick a heater, small pump to circulate the water and a digital thermometer. Turn the heater temp above the ambient room temperature and see if the temp fluctuates.