It's 150% total, so +50% increase.
Viewing post in Small On Top 0.19.01 bug fix comments
Wow thats a lot wtf, I remember there is a npc that talked about penetration being multiplicative, so let me be guess, the % bonus to stats is addative to other percentages in the case of buffs? Lets say Lace has tempest rush active (+50%mag), used vortex twice (+50%mag) and has rubyros flare (+%5 to magic damage) it will calculate: total mag+100%mag buff>ability scaling>final ability damage increase by 5%?