He didn't have it backwards, he was saying the same thing as you. He said, "suppose you had a clock that counted seconds," then described how it would work (it

He didn't have it backwards, he was saying the same thing as you. He said, "suppose you had a clock that counted seconds," then described how it would work (it would be a non-multiple) if that was the case, which it isn't. You ignored that his description of the behavior was part of a hypothetical and not meant to describe how it actually behaves.