The shards needed for a guaranteed lego is the same with or without x2 event.
U need open 200 shards to start add % to the lego chance. Until then u will have 0.5% or 1% each sigle time, until u reach 200 shards (if u werent lucky and got one in the way trought, in that case the count reset and start from zero again).
After the shard 200, u gain 5%. So 200 +19 is = 0.5% or 1% + 95%, almost 100%... not 100%.
I u want 100% guaranteed, u need that extra one... so 220 for a single guaranteed lego, with o or without x2 event.
As simple as that.
Again... u must be really unlucky for be in this situation...
I swear I am in that situation, been a year+ since my one and only void lego. And I pulled 50+ in last 2 weeks.... argh