Some question about the element forming Cost Function

Is anyone can explain why the number over the summation symbol is ‘m-1’ rather than ‘m’?

Opps! I think I figured it out. It depends on the number beneath the summation symbol. When it is ‘i=1’, the number above the summation symbol is ‘m’. While in Python, the range of vector elements starts from ‘zero’, thus the cost function can be changed to ‘i=0’ beneath the summation symbol and ‘m-1’ above the summation symbol.

That is correct @Sam_Science