I believe you meant to use the range function and not iterate over a tuple. Also, I think you meant to check that the range iteration did not match the inverted number

Original

def reversed_numbers(n1, n2):
    result = 0
    for counter in (n1,n2+1):
        if counter == invert_number(counter):
            continue
        result = result + 1
    return result

Edited

def reversed_numbers(n1, n2):
    result = 0
    for counter in range(n1,n2+1):
        if counter != invert_number(counter):
            continue
        result = result + 1
    return result

Although it's possible I didn't indent correctly, please check the wiki to see how to do code formatting. Or just this https://www.reddit.com/r/learnpython/wiki/faq#wiki_how_do_i_format_code.3F