If you are looking at what I think you are, which is a photocopy of the masters register ( I saw the original held at Guildhall library), columns in order are, from the left:
1st small column, usually nothing in it
2nd column Name of captain
then 4 columns all headed 'certificate’, 1st is number, 2nd where received, 3rd year, 4th special qualifications (usually empty)
The next column in this volume has a newspaper-like cutting stuck in with glue, which gives the mariner's full name, his place of birth& a few other details, obviously cut out of some other publication.
The columns beyond this are for each year - so in the example I’m looking at, the first column is for 1869, the next for 1870 & so on. In these columns is given details of the ships & voyages that the captain served on, I believe; and details of any key incident that happened to the mariner - his death for instance.
Copy of teh page I;m referrign to is attached.