Bad Luck drop bonus, how it works?

Question

We can see information from Make Believe quest on boss tab saying "Bad luck drop bonus xx.xx%", how it works?

Is this one related only to Moonsilver items or also other valuable items from bosses?

What if it reach 100%? Is it still not enough big bonus for guaranted item?

Answer 1

100% just means 2x what the original drop rate was. If your chance of an item was 2% 100% bad luck means 4% chance.