Aran attack decrease per mob hit

1 mob = 100%
2 mob = 70%
3 mob = 60%
4 mob = 55%
5 mob = 52%
6 mob = 50%
7 mob = 48.57124285621428%
8 mob = 47.5
9 mob = 46.6%
10 mob = 46%
11 mob = 45.45%
12 mob = 45%

* IT applies for all Aran skills/ attacks.

I don't know if this is already solved, but I've found that out myself since I've bored.
This is the percentage of attack being dealt when an aran hits the amount of mob listed above.

There must be some kind of formula for this I suppose, since it goes by an ordered decrease amount. (Will try to solve this later)