The temp controller basically unplugs your fridge/freezer, so whatever side your probe is on, when the proper temp is reached, both sides will turn off.
just reread your post. I would put the probe in the freezer set at 35, and put a thermometer in the fridge side, wait 24 hours then you will know what the temp will be for the fridge. Normal fridge temps are around 35-40. Good luck with your project!