Last Comment on the Meal Last Night

In preparation for cooking the Thanksgiving meal last night, I had done my conversions from Fahrenheit to Celsius. When we lived in Germany I had the formula to figure this out hanging on the refrigerator since our oven dial had Celsius temperatures on it. As I went to pre-heat the gas oven at the B&B and I was faced with 1 through 9 on the dial. What is this? Here is the history.