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