1st circle (provs 2-5)
Bureaucracy modifier – 0, i.e. province efficiency is not influenced in a negative way by its location.
2nd circle (provs 6-13)
Bureaucracy modifier – minus 0,2, i.e. the province efficiency in the second circle is 20% less...
3rd circle (provs 14-19)
Bureaucracy modifier – minus 0,4, i.e. the province efficiency in the third circle is 40% less...
So 70% efficiency is correct 100-30 = 70% --->
5th annex -50 -20 (2nd circle penalty) = -70 +your 40 (bureau lvl8) = -30
You just need more bureacrats in your empire
Wait till you get to 3rd circle, then it gets tuff