How does threaten work?

assumming chaos vellum, is it

300-30=270% PDR
or 300*(1-0.3)=210% PDR
?

aditionally with the hyper, which of these three is the correct way?

300-50=250% PDR
300*(1-0.5)=150% PDR
300*(1-0.3)*(1-0.2)=168% PDR

Those are the correct values for PDR hypers.
This thread: http://www.southperry.net/showthread.php?t=72874&p made me disprove my friends theory & it didnt match if it was a pure 50% line, thus making 30% 20% lines separately the correct answer.