Guild Wars 2

So it gives % damage foes below 50% hp, now my question is, does it adds up when you wear more runes at once like 2 pieces give 1%, 4 gives 2%, 6 gives 5% (might not be correct but doesn’t matter) so does it give 8% or 5% damage inrease with all pieces?

It should stack, wearing the full set should give you 10% more damage vs foes below 50% HP.