If you insulate the probe with foam and put it next to the side of the fermentor you will get a more accurate gauge of the temperature.
An alternative is to wrap the probe in a ballon or latex glove, seal it, and then place the probe into a pint or quart of water.
This will keep your freezer from turning on and off frequently.
My setup turns on for about 10 minutes every 2-2.5 hours.
If your using the 2nd method, during the initial and very active fermentation stage u will need to cheat the system a little because the prob is reading the water in the container and not the actual temp of the fermenter.
I use the second method because my probe isn't long enough to reach the fermentor. So if my target temp is 68F I set my controller to turn on > 65F. The water temp in mason jar I use will read 65 and the fermentor with the active fermentation will read my target temp of 68F. After 3-4 days I will change the controller to the set mark of 68F.
Different brews with higher / lower gravities and different yeast will have different scales, so you can adjust accordingly. But if i'm within +- 3F i'm a happy camper.