I've made a new conversion, but the numbers are wrong, what causes this?

A. ConvertEasy needs to know the values of two equivalent points on each scale. These numbers must be equivalent - that's very important. So for example, I could set the minimum value of the top or left scale to have a value of 0 degrees centigrade, and the minimum value of the bottom or right scale to have a value of 32 degrees Fahrenheit, as these two values are equivalent, that is, they represent the same temperature. The corresponding values of the maximums could be 100°C and 212°F respectively, as these two values also represent the same temperature. Instead of minimum values of 0°C and 32°F, I could have chosen -40°C and -40°F, as these two values are also equivalent. It doesn't matter what values I choose, as long as they are equivalent on both scales. If the minimum and maximum values are equivalent on each scale, then the conversion will be correct.