Using hashcat with maskprocessor - here: veracrypt

[Snoop]

you need to add --increment too
the --increment command line switch enables the increment feature (and min/max options are further restrictions/limits)

Thank you Phil !

Code:

hashcat -a 3 -m 13711 part_I_remember?d?s --increment --increment-min=4 --increment-max=6

I'm going to try it!