Brace Height
What is the brace height? It's the distance between the string and the deepest part of the bow grip.
In our previous post, we showed you how to mesure your bow length and how to have to right one for you. Here you will need to know it to determine what your brace height should be.
Bow Length → Brace Height (Min - Max)
64" → 8" - 8 3/4"
66" → 8 1/4" - 9"
68" → 8 1/2" - 9 1/4"
70" → 8 3/4" - 9 1/2"
Remember to mesure your the brace height as often as possible (using a bow square - T) as it can change if the string untwists itself.
Hope this answered your question!
Source: http://www.lancasterarchery.com/blog/what-is-brace-height/