Set Min and Max Password length give error

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I can't really imagine myself cracking such long passwords, but in your case, I recommend you to generate one wordlist with numbers length of 10. Randomize it, then split to sizes like 10MB or so and use that in combinator attack. Combinator attack uses two wordlists at once, so you could play with and understand a bit. By having two wordlists and combining them together, you will get the length of 20.

Read more about combinator attack: https://hashcat.net/wiki/doku.php?id=combinator_attack
Mask processor: https://hashcat.net/wiki/doku.php?id=maskprocessor