The next verse makes it clear that Nephi is abridging the record of his father. Many of the visions and prophecies of Lehi would likely have been recorded in the book of Lehi which was lost with the 116 pages (see D&C10). Nephi doesn't have room on his plates to rewrite them all. This also helps us to distinguish between 1 Nephi and 2 Nephi. The former was an abridgement of the record of Lehi (with a lot of personal additions from Nephi). The latter was Nephi's own record.