juggernaut unbreakable 5% reduced damage taken

One of the boni from the unbreakable node for juggernaut saits '5% reduced damage taken'. So if this said '5% less damage taken' this would simply be multiplicative and be equivalent to 5% more life (1/0.95-1 for the math nerds). But reduced means it should be additive with other forms of reduced damage taken. Which means what exactly?
If the damage is elemental it should be additive with the '8% reduced Elemental Damage taken while at Maximum Endurance Charges' from unrelenting and similar mod from Nebuloch mace.
Is it additive with physical damage reduction from armor/ endurance charges?
Or there are other sources of reduced damage taken or reduced chaos damage taken?
Finally does this actually mean 5% reduced where if you had 100% reduced you would take zero damage or is only the 1/(1+0.05) you get with things like cool down reductions?

reduced damage taken happens after avoidance (evade, dodge and block) and mitigation (physical damage reduction and resistances). it is additive with other sources of the same mod, including shock and fortify. some of mods specify they work only with hits only (no effect on DoT)

you can consider it "less" only when you have no other such modifiers