Another Oddity

Just one of those odd constructions.

"That academic article used so much jargon. I didn't understand 20% of it!"

Okay. How much did I actually understand?

A. 80%.
B.  Less than 20%.

What if I would have added "even?"

"That academic article used so much jargon. I didn't understand even 20% of it!"

What if I would have done this as most people would with the "even" before the verb?

"That academic article used so much jargon. I didn't even understand 20% of it!"

When I said this, I meant that I understood less than 20%, but the friend I was speaking to assumed I meant I understood 80%.
Just an oddity, but to be precise, I would have to probably add the "even"-- "even 20%."

And we should be more precise in our writing than our speaking, right? I sure hope so, because obviously in speaking, I'm imprecise!
Alicia