TVS diode electrical parameters
They are saying two things.

Firstly, if testing the device (on its own) with an ESD gun conforming to IEC 61000-4-2 then it will survive a 16 kV discharge test. It's listed in the absolute maximum ratings section and this is generally what that section defines. It doesn't tell you what it will clamp to but it'll be in the order of tens of volts

Further down they are saying that it will clamp a 6kV discharge to typically 7V when used with the same ESD gun. This gives you some confidence about performing in-circuit testing and what sort of voltage levels you may witness when doing ESD testing.