Scouring Winds ascendancy node

Does anyone know how this node works (or is supposed to work at least)?
"Exposure you inflict lowers the affected Resistance by an additional 20%"
Does this increase the base exposure value to 40% resulting in 10% increased exposure effect adding 4% lower resistance or is it added after the increased exposure effect calculation?

If anyone else wonders the additional 20% from Scouring Winds gets added to the base exposure value.I`m using it atm with 25% exposure effect increase and that results in 50% exposure.