As far as I know (anyone correct me if I'm wrong), yes you'd get 400 at the end of the year and that's if you put all your stake reward into a unstakeable address -spendable only. However , if you keep those coins that you minted in the staking system it obviously keeps increasing the amount of staking weight you have but still at a 20% interest - so as to say it compounds upon itself. So you wouldn't have 2400 coins at the end of a complete years stake starting point, but rather more coins because you continued to stake the new coins you minted on top of the original 2000. I'm no math wiz but I'm sure there is a formula that could calculate a true value based off original coins at a staking starting point and a projected total at a certain future date based off staking the new coins you mint.