Reliability where N is the number of nines:
1 - 10 ^ -N (multiply by 100 for percent)
So 9% is 0.09 for the calc
1 - 10 ^ -N = 0.09
So
10 ^ -N = 0.91
So
N = -log10 0.91
So 0.09 (9%) reliability is 0.0409586077 of a nine.
And running it thru... a tenth of a nine is 0.2056717653 or about 20.57% reliability