You work in an airconditioned office. The thermostat for the airconditioner is set to 23.5C. The thermometer gauge says that it is currently 24.2C. Do you:
A) Ignore it;
B) Close the door to the stairwell that all the cold air is escaping down;
C) Set the thermostat to 21C so that it gets colder. After all, it should go down to 21.7C, right?