What do you mean by 12' s corresponding qualifications and experience within five years when he was promoted from second pipe to second pipe?

Reach the valid qualification of 12 months within 5 years. According to the information in "Rules for Certification of Seagoing Crew Training Examination", when applying for promotion to large-scale ship examination, Class II ships must have 12 months of effective experience on board within five years, and apply for Class A large-scale ship examination in infinite navigation area, and Class II ships should also work in infinite navigation area for more than six months.