Clerks making record copies of documents often encounter errors or inconsistencies in the original record they are recording. In the days when transcriptions were made by hand (or by using a typewriter), clerks would often annotate such things. In the illustration, the typist has underlined known errors or inconsistencies in the original document. These notations used by clerks can vary–lines may have been written above questionable text as well.
The clerk’s job was to transcribe the document exactly as it was written–errors and all.