Help decifering a WWII Merchan Seaman medal roll

I'm researching a Percy C. C. Stockbridge, formerly of the East Kents and ASC during World War I, who won a some sort of Merchant Seaman medal during World War II.

I've found him on the Registry of Shipping and Seamen's WWII medal roll at the British National Archives, but have no idea what any of the numbers and abbreviations circled mean. And do the dates mean date of birth? Can anyone help? Percy is at the very bottom of the list.