"New users can only upvote and downvote with 100% voting strength.

Once you reach about 500 STEEM Power, you will see a vote slider appear when you vote. You can use the slider to adjust the weight of your vote, between 1% and 100% voting strength. Voting with less than 100% voting weight will use up less voting power, but it will also have less of an influence on the post or comment's rewards."

That's from FAQ. I am close. :)