The account creation fee is 5 Steem, and when the account is created, that 5 Steem is "Powered up" into Steem Power. That means it can't be immediately pulled out of the account without a time consuming "Power down" process, but as long as it's in Steem Power instead of just Steem, it can basically accumulate interest. That's why your account now shows 5.004 Steem Power instead of just 5.