Need Rylai's clarification for Vel'koz W

Which type of slow category is W?? Is it two separate instances of "instant aoe" for 40%? or is it a "DOT" for only 20%?

My unbiased opinion as a main is that it should be 2 separate applications of 40% slow, otherwise the item is entirely worthless for slows on him now (because slows no longer stack, and his Q and R already have their own slows).