There is currently a small issue with PoS that will be updated soon that will increase amount of PoS payouts (currently not giving full 15% per year). But the reason you only stake 11k is because of your deposit size.  It always stakes each deposit seperately.  Sometimes you may even see it stake more then one block at a time with more then one stack of coins (if all of your deposits were around 11k then everytime you stake it will be 11k per block staked)