Temp variation on controller

[lovemybrew]

I recently added a controller on my old fridge, and discovered there's a 4 degree variation between the setting on the controller and the actual temperature. And trust me, I checked it with several different thermoters, including digital.

Obviously, if I know about it I can adjust for it. Just wondering if this is common, or if I should return it to my lhbs?

 

[chemman14]

what kind of controller is it? If it is analog there will be a 3-4 degree swing in the temperature. If it is digital you can set this differential