Just a warning me found out today from SuperCOin. SilkCoin has 2 billion MAX possible in the code. SUggest everyone to review the code
This is nothing unusual. All full PoS coins have a large Max Supply, that is there to account for the annual interest earned by staking.
It doesn't mean that is the number of coins that will be minted, it is just a hard cap for the maximum number of coins that can be generated through PoS, not that it will be reached anytime soon. The same is done for Peercoin which has a hard cap of 2 Billion coins