you are using the bruteforce attack without a mask/maskfile
hashcat.exe -a 3 -m 1000 -i --increment-min=13 hash.txt ?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a
or put the 15 ?a inside another file (mask.txt) and run
hashcat.exe -a 3 -m 1000 -i --increment-min=13 hash.txt mask.txt
this would test 13-15 positions with complete upper, lower, digits, special charset starting with 13 positions
another approach would be a dictionary attack with rules/and or single rule truncate at position 13
jfmi why/how are you knowing that the password is exactly 13 chars?
hashcat.exe -a 3 -m 1000 -i --increment-min=13 hash.txt ?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a
or put the 15 ?a inside another file (mask.txt) and run
hashcat.exe -a 3 -m 1000 -i --increment-min=13 hash.txt mask.txt
this would test 13-15 positions with complete upper, lower, digits, special charset starting with 13 positions
another approach would be a dictionary attack with rules/and or single rule truncate at position 13
jfmi why/how are you knowing that the password is exactly 13 chars?