As long as remember and since i met them they are only 2 nine duans in China.
Duans ,expect for chen taiji self made duan, were made by the government as a standart point of reference.
It is pretty new and amongs shaolin monk the highest duan is 7...
duans depends pretty much on the numbers of student like 30 for 1, 100 or so for third.
passing fourth requires demonstration of skill
also you need to have attended some competition
sixth duans require you write some reference book and practice for 15 years..
ect etc
more books more student more years in the joint...
duans are not very important but they should also not be neglect

in shaolin people use tatoo some dots on their head showing the level of skill they had attain....
well, it is all about recognition....