...Under "Operating Instructions" part "B: Charging battery outside of vehicle", it says you have to attach an extra jumper cable to the negative battery post, that is then clamped to the charger's actual negative cable. See below:
Both my charger's instructions and these look identical on this point (Indeed, they might be the same instruction sheet).
Why is this extra cable needed?
(Not like I don't have one, just rather curious...)