This type of t/stat is not officially adjustable and needs to be replaced if out of calibration.Be aware that if your oven only has top and bottom heaters and no circular heater at the back the t/stat will be compensated to allow for the excess heat from the top element close to its probe therefore if the top element is not heating the probe will wait for this excess heat to arrive from the bottom element causing the oven to o/heat.Check top element before changing t/stat
Kenjo
March 2012