The reason your temp overshoots the set point is due to the thermal storage in the coil.
Basically what happens, is the hot water heats the tube and that in turn heats the surrounding beer. All of this heat transfer takes time.
As the beer heats up, the sensor identifies the you are at the set point. And shuts the pump off. But the liquid between the coil and Thermowell is actually hotter at that moment and time. You also have very hot water in the Tube, and the Tube it self is close to the hot water source.
The latent heat in the Tube it self + water in the tube + gradient from the Coil to the Thermowell will slowly dissipate and continue warming the adjacent beer.
While the fermentation is active, the mixing balances this temp out. But in this case your fermentation is not active.
As a general rule of thumb, we have found you should keep your "heat water" no more than 10F hotter than your target temp. So, if you are targeting 68F, you heat water should be 78F. . . . that will minimize the over shoot you are seeing.