If I lose 6 cents of a 12 cent investment, I make that a 50%...

If I lose 6 cents of a 12 cent investment, I make that a 50% loss. If I lose the whole 12 cents, then it's a 100% loss. Fortunately, as a shareholder, you cannot lose more than that (but that is a good reason to think very carefully before getting involved with leveraged investments).

So to answer your question, if it goes to 2 cents (from 12), you have 2/12 (2 divided by 12) of your investment left, or 16.67%, which means you've lost 83.33%

Not that I think it will go that low... but we'll see.

(Actually, from my dim memory, I think your way of looking at percentages is the way retailers do it, so when they say a 50% markup on goods what they really mean is that 50% of the retail price is their part, but what most people would think of as the cost plus 100%. But they probably express it that way so they don't sound too greedy.)