Colonist Instant Kills

[Rimstrong]

Trying to understand this setting.

"Colonist instant kills: Adjust the chance that a colonist can die instantly due to an attack. The incoming damage is adjusted so it will down the colonist instead."

The slider is 100% to 0%. Question is, % of what? Does setting that to 50% reduce the incoming damage of blows that would ordinarily kill you by 50% or does it mean half the time a shot that would of killed you, does, and half the time it just downs you.

And then it begs the question, if you set it to 0%, does that mean you can't die from attacks (only from other means, like blood loss, etc)?