How nonlocal keyword works?

In the below code,

def makeAverage():
    series = []
    def average(newValue):
        series.append(newValue)
        total = sum(series)
        return total/len(series)
    return average

python interpreter does not expect series to be nonlocal in average().

But in the below code

def makeAverage():
    count = 0
    total = 0
    def average(newValue):
        nonlocal count, total
        count += 1
        total += newValue
        return total/count
    return average

Question:

Why python interpreter expects count & total declared nonlocal in average()?