Clarifying the epic potential scroll

Gives Epic Potential to items that are ranked Rare or below. Once potential has been added, a magnifying glass can be used to see the hidden potential. If it fails, the item has a 20% chance of being destroyed.

Logically, this means

80% success
16% fail, nothing happens
4% boom

But Nexon could have typed it wrong and it really means

80% success
20% boom

What I want to know is

1. How does it work in KMS?

2. Does anyone have proof or reliable source of using an epic potential scroll in GMS and it failing and the item not booming

3. If the 16% fail does happen, does anything else happen besides losing the scroll?

4. For clarification purposes, these scrolls can be used on 'rare' items and 'non-potentialed' items correct?