Steemit Inc. delegates some Steem Power to new accounts. It can fluctuate, because they will decrease their delegation to you, as you gain more Steem Power for yourself, participating in the Steem network.
It can also fluctuate, because of the fact that the amount of Steem Power you have will automatically increase over time, without you doing anything. This also applies to delegations.
ok, so it's nothing that I can adjust or change other than to go 50/50 or all steem power?