reduced extra damage from suppressed critical strikes

I'm looking for confirmation of my understanding.

for example:

say (spell) base dmg is 100
crit multi is 150%, so crit dmg is 150
suppressed dmg would be 150 x 1/2 = 75, yes?
(meaning not just base dmg is halved, but extra crit dmg as well)

now, if I have "take 50% reduced extra damage from suppressed critical strikes" (from passives tree), would my dmg be:

(100[base] + (50[crit] x 50% reduced)) x 1/2[suppressed] = 62.5 ?

so (assuming a crit multi of 150%) this passive/mastery reduces my dmg taken from spell crit hits from 75 => 62.5, i.e by ~17% ?

thanks!

helm