Why is there a degree symbol in Centigrade and Fahrenheit or why is there a small circle above on the left hand side of letter C and letter F?

The small circle is the symbol for degrees.  These are both measurements of temperature, although the value of a degree in one is different than the other.

Freezing is 0 degrees Centrigrade and 32 degrees Fahrenheit.  The boiling point of water is 100 degrees Centigrade and 212 degrees Fahrenheit.  As you can see, one degree represents a greater change in C than in F.  The actual formula is:

(F - 32) x 5/9 = C

Even though they are different scales, in both a degree is a measure of the change in temperature.