Recalculating Fire Nova Mine Tooltip Dmg

Hi,
I need your help finding a mistake in my calculation.
My FNM deals 181-271 base dmg, my weapon has 21-42 flat fire spelldmg
and I got %increased dmg = 674%, spell effectiveness on FNM is 30%.

FNM tooltip shows the dmg of the first wave so the more multiplier can be ignored.
My calculation:
(181+271+0.3*(21+42))/2 *(1+6.74)=1822

The Tooltip shows 1704.5 though.

Tyvm, trying to figure this out for weeks now.

Still looking for a solution to this,
my gear:

Passive Tree:

Screenshots from offline skill tree planner with imported gear:

bump

+

the tooltip could be affected by cast speed

Hi, it's not affected by castspeed, just tried it with the support. I get a higher dmg value from my calculation so there must be something that goes into calculation but does not work with mines, maybe even a bug.

alright, Id ask first where does your %increased dmg = 674% come from

is it all increased damage you have, more damage from controlled destruction + crit, all combined into one multiplier? are you sure it is correct?

The base dmg (min-max fire dmg) that I can read out from the tooltip is calculated without including critical strike chance. Crits are going into calculation after that and only show up in the "AVG. DAMAGE" on the tooltip.

The %Inc-Dmg 675% is combined inc dmg from passive tree, jewels, my gear and also the % from quality support gems linked to FNM (10% firedmg from firepen, 20% firedmg from fnm, 10% inc spelldmg from controlled destruction and so on).

I checked it manually and by importing all my gear into the poeoffline skilltree.

http://docdro.id/0n2FUgT is the whole calculation, it is getting very close to the actual tooltip value but the basedmg is wrong.
Basedmg from my calculation: 3222-4905
Basedmg from my tooltip: 3195-4863
So the difference is smaller the more dmg modifiers I use in my calculation.