Dang I have a master's in math, and I can't understand these shenanigans here without sitting down and giving it deep thought. I'd just stay away from financial instruments like this one. Maybe the bank should make their customers pass an IQ test before they give loans like this one. The loans do seem likely to fail for a great many unsuspecting people.
It really is hard to beat the bank, which is why it is better not to try, and instead, use them as little as possible.