How i arrange pass for BF?

Good days to all.
Frstly many thanks for very useful tool..

I try brute force attack with oclhascat, but i'cant arrange pass

I want bf begin with 8 character and ends with 16.

i use this command


but this command begin with "a" i think.

this command must begin "aaaaaaaa" and must continue like this "aaaaaaab, aaaaaaac.......aaaaaaa1.......
and must end "zzzzzzzzzzzzzzzz"

How i arrange that?

Regards....