Skill level up stack?

When you level up a skill. Does the dmg % stack up or does it replace the previous %?
Like say if a skill says “inc add dmg by 20%, 30%, 50%”, does it add it all together so 100% more dmg or is it just 50%?

Yeah can a slayer get this question answered please

The first rank says increases damage by X%, then each subsequent rank that also increases damage specifically says ‘increases damage by an additional 30%’ or whatever the number may be. This for sure implies that they all stack up, and if you look at abilities that increase things like HP or defense, they always add up to a clean number when you stack them all. for example, my veteren ability adds up to 10% less physical and 20% less magic damage at max rank.

The language definitely implies that they add up, and if they don’t, then its very misleading.