I want to shortin my brace height 1" how much do I lng. my string? It is 63.5"

Just twist it a few more times and then check it.

Good question... I just made a too short string myself...

I would UNtwist the string about 12 rounds and check it.  If you need a longer string PM me if you shoot Dacron, I can make you one.

I read your question wrong.  I wouldn't untwist it too much.

Just be sure you have a few twists (I'd go with at least 6, 12 is better) in the string when you're done. If you can't untwist enough, you may need a new string.  All that being said, I would not assume a number for my brace height and go with it.  Don't just shorten the brace height because you think where you are is too high.  Paper tune to find out the proper brace height and go with that.