Maul’s Seething Rage “subsequent uses” clarification

I don’t have him unlocked yet, so I can’t test, but typically increases are additive not multiplicative. In other words:
A: 100%, 160%, 220%, 280%, 340%
Not B: 100%, 160%, 256%, 410%, 655%

I believe it’s worded how it is because if it just said this: “Each time this ability is used, it deals 60% more damage on subsequent uses”, that could be interpreted as: 100%, 160%, 160%, 160%, 160%.