Voluum ( or any tracker ) traffic loss function.

(same time zone, same time range), Galaksion 40k impression, Voluum 20k...In Voluum traffic loss set up at 20%...galaksion dashb costs=28usd , Voluum 24...numbers dont match to me ..so how should I set the whole up to make numbers match?. This have been discussed before but why Galak has such a traffic loss compared to