Merchant Navy - Help me crack the code

I have my ancestor, Charles Vollett, seaman's ticket (attached) but to take my research on his merchant navy career further I need to crack the code contained therein.
I have found the UK and Colonial ports codes on the National Archives website (he appears to have sailed from Plymouth (his home town) and Exeter), but can find no reference anywhere to the foreign port numbers and what the rest of the Voyage details mean
If someone could tell me what the numbers mean in the 1851 and 1852 voyages columns, I would be very grateful.
Many thanks
tessacate
I have found the UK and Colonial ports codes on the National Archives website (he appears to have sailed from Plymouth (his home town) and Exeter), but can find no reference anywhere to the foreign port numbers and what the rest of the Voyage details mean
If someone could tell me what the numbers mean in the 1851 and 1852 voyages columns, I would be very grateful.

Many thanks
tessacate