wire chart ?

[cooper]

I am sure it is just me but in the study hall wire size chart, why is there a difference between the mm 2 and the cm 2 ? for example 16 guage is bracketed as 1.31 mm 2 but in the next column it has 2,336 cm 2 . What does this corelate too ? I have rolls of wire here at work that are of a standard automotive size for light runs and it has .75 mm writen on the label. What does it all mean...........