That sounds like an old document.

They changed it to 12 weeks to power down completely awhile back. It pays you every week for 12 weeks. IF you did nothing with your account it would be completely powered down in 12 weeks. You would receive 12 payments of steem once per week.

When you initiate a power down (give it a shot, you can cancel it... it won't actually do anything if you cancel it before 7 days when the first payout occurs). It asks you how MUCH of your steem power you wish to power down. The default is the maximum you have at the time of the power down.

So if you had 1200 steem power and you said to power down 1200 steem power and you did absolutely nothing else with your account you would receive 100 steem per week for 12 weeks.

If you did things that gave you more steem power that would not be included in the power down.

There is no conversion fee, only time.