Math question on Blade Dancer

Boost is 1/2 of total correct (2to1 ratio)

So if there is a total of 249 for all the armor on the other team - that is 249/2/4 +20 correct? (which I would have thought the case would be)
or is it
249+20/2/4 (which is what it seemed to be at 31 points per troop )

Would be 249/2 + 20, scattered among 4 targets. 249/2 is 124, add 20 for 144, split up but not always equally.