A pirate's impressiveness and first-impression strength is usually dictated by the bounty he or she earns. Therefore, the higher the number, the more fame and respect the said pirates receive. Any rookie pirates who manage to receive a bounty of over 100,000,000 before they enter the New World are considered to be impressive, as it marks that said rookie has committed criminal acts of catastrophic degrees. However, once past the "Paradise" half of the Grand Line, bounties of around 100,000,000 are considered common and even weak.
While bounties of 300,000,000 are highly impressive, a pirate with one can still be considered a rookie. A pirate may ultimately shed their rookie status after several years of regular pirating activity.