I came up with 13% based on what I had available to me, being 1% off doesn't seem embarrassing.
When you're being an ass and telling someone to learn math before they open their mouth, only to then get it wrong ... you should be embarrassed.
Given that you were talking about how criticals could be abused you should in fact have taken the max value, meaning you were closer to min 6% and max 9% off, depending on target luck.
Lessons learnt:
1. Don't be an ass.
2. Don't say "learn math" when you are not in full command of the figures.
3. People can be embarrassed for you, even if you do not have the good grace to feel the emotion yourself.