[__s]

By seed you mean salt. Salts are stored in plaintext, so they don't increase the entropy of the password. Instead they make it so that each password hashes uniquely so that everyone with the same password gets different hashes. They also mitigate rainbow tables by effectively requiring the attacker to create a rainbow table per target

[i-am-curious]

Yes I meant salt! AFAIK such a fast cracking of hashes is mostly via rainbow tables, salts defeat those easily.