Mortal wounds in addition

[frostfire]

Some weapons, says the poleaxe of Hearthguard berzerkers, have the ability to do mortal wounds in addition to normal damage on the unmodified hit roll of 6,

Does it mean  for each unmodified hit roll of 6 that's additional mortal wounds on top even if I fail to do any normal wound

or do I need to make successful wound rolls for each of these attacks to do mortal wounds? 

[SolomonHelsing]

Yes it means additional mortal wounds on top even if you fail to do any normal wounds.

It just means that you still get to roll to wound for each of those attacks after. Rather than it causing a mortal wound and that attack ending.