Block explorer currently 18644998.20237726 outstanding coins.
http://explorer.ghostcoin.org/chain/GhostCoin

Coinmarket cap is calculating the number of outstanding coins incorrectly. It is taking the total of combined PoW + PoS blocks and multiplying them by the reward amount.

It should only take the total pow coins and multiply that by 4000.

The official block explorer will show you the correct amount.