I looked through some other nearby pages, and I believe that the initials correspond to the area in which the person lived or church that they belonged to. I.R. would stand for Indian River, and C.S. would stand for Cool Spring. Other areas/churches with shorter names are spelled out, such as Lewes and Rehoboth, as you can see on previous pages. In addition, you list the birthplace of John Dutton as Broadkiln Hundred. This was a latter spelling of the name. At the time of his birth, the area was known as Broadkill Hundred. It was changed in 1833 to Broadkiln, although it is still referred to as Broadkill Hundred as well.