This is from another thread but the poster says he is with KMC. He has very informative posts about chains.
Originally Posted by
Papa Ado
The easiest and most convenient way to check chain elongation is at the rollers which also includes other chain wear at the inner link sleeves and pins. It's not perfect but most users won't measure actual chain length so that is why we suggest 0.8% and offer "easy chain checkers" and "digital chain checkers" for most users.