I am not sure of the reduction amount, but one think I do know is
no sugar is added to true boiled cider.  Just as you would not add sugar to maple sap to make maple syrup.  My grandmother has a very very old supply of boiled cider, which I still have, and my Father made a pie out of it about 8 years ago.  He said it was a 40 to 1 reduction but he may be thinking of maple syrup.  I think that I read some where that it was a 10 to 1 reduction.  But one thing for sure  NO sugar.