Penence Brand calculation question.

So, if I want to calculate the exact damage a brand would do from first applied til it drops off, would this math be correct for this or do I missunderstand something.
(Numbers are jut made up its the concept)
At stage 1 my brand does 400,000 dmg, at stage 2 it does 500,000 stage 3 600,000 and so forth.
Would I then add all these together like 400k+500k+600k+ all the way up to 20 stages.
Then my brand has 25 activations per brand so at 20 stages I take max damage 5 times and add all these together for a full DAMAGE calculation of the brand?

I do NOT care about DPS here, I want the damage PER brand.

So to shorten it, i take stage 1-20 add all these numbers together, then stage 20 I take 5 times more and add together for 25 ACTIVATIONS per brand?

Cheers hope someone knows and even understand what I mean.