Hi! When you joined the steemit, you were given 0.5 SP as a gift, and 14.5 SP was delegated by steemit for you. Lets say it's a loan to induce your carrier.
As you started using the platform and earned some SP on your own, it will be added to your SP and steemit will reduce the delegated SP by - more or less - the same amount. When you have earned 14.5 SP, the delegation is over and your SP will increase.
RE: What exactly is delegated STEEM power in my wallet?