I'm puzzled by the fact that I can see a Postings column. According to information from Nat. Archives you shouldn't be able to see this.
9.4 The ‘postings’ column
Each entry in the Register extended across a double page spread. However, the accessioned digital record does not include the ‘postings’ column on the right hand page which contains various codes used for National Registration and National Health Service purposes. The National Archives does not have access to this column and the information it contains.
So how did you access a page with a Postings heading? Is this definitely from the 1939? Can you tell me who you were looking at?