Extension of Validity of Seaman Book

There are 2 columns for extension at page 8 in the Seaman book.
The validity of each columns for extension is 2 years.
Seaman book has to be renewed if both columns had been used.
The Seaman personally or the Seaman's employer on behalf of the Seaman (shipping Company) must come to the Embassy to submit the expired Seaman Book for extension.