Yeah, so the mask (the ?1?1...) has to be at least as long as the minimum length of the plaintext you're trying to compute. Each ?<something> stands for one character in the plaintext. For a plaintext of 8 characters you would want:
?1?1?1?1?1?1?1?1
If you knew the first 3 characters were the string "abc" and you only needed to brute-force guess the last 5 characters, you would do the mask like this:
abc?1?1?1?1?1
If you knew the last two characters were @$, but needed to brute-force the first 6, the mask would be like this:
?1?1?1?1?1?1@$
Make sense?
BTW if you're trying to do SL3 unlock then you need to use the binary character set as atom described (00010203...).
?1?1?1?1?1?1?1?1
If you knew the first 3 characters were the string "abc" and you only needed to brute-force guess the last 5 characters, you would do the mask like this:
abc?1?1?1?1?1
If you knew the last two characters were @$, but needed to brute-force the first 6, the mask would be like this:
?1?1?1?1?1?1@$
Make sense?
BTW if you're trying to do SL3 unlock then you need to use the binary character set as atom described (00010203...).