Grove High Temperature Sensor

This sensor's official Arduino library comes with abysmally bad hard-coded calibration, and zero documentation on how to fix it. The measurement granularity is terrible (it changes in increments of roughly 2.3 degrees C) and the accuracy is worse. Despite the claimed 2% +2 degrees error, mine is firmly declaring that my workroom temperature is 42.95 degrees Celsius (it is 19, that's an error of 23.95 degrees) and my armpit is 51.94 degrees (it is 36.3, error = 15.64 degrees). I have considered taking an anal reading, but first I would need to track down the people responsible for marketing this device.