Hmm, this has to be a +, not -. I have certainly mistyped in the hurry. The formula cosists of 2 parts - the initial calculation and the secondary factor (quests and hero level)
Initial calculation (1st part):
100+((100-18 )*4)= 428
You have have:
Level 57, quests 86 = 143 total
now we factor in the 2% into the initial calculation and then the quests + level (2nd part):
428*0.02 = 8.56 * 143 = 1224.08
1st part + 2nd part = high score:
428 + 1224.08 = 1652.08, rounded down, 1652.
I hope that clears it up

It certainly cleared it up to me once again

I have forgotten how it was, haven't been into KBAP for some months now - but when crossworlds comes out, I'll install it again.