The Anthon transcript is the oldest copy of the supposed Book of Mormon writing. It may not be the actual copy taken to Anthon as Whitmer wouldn't have been on the scene at that time to have seen just what was taken to Anthon. Anthon describes the text as being in long columns.
It may be that Smith or someone made another copy and copied the lines horizontally. So this copy must have been given to Whitmer by Smith, or shown to Whitmer by Smith, when Whitmer got involved in the Book of Mormon and Whitmer assumed it was the same one that was shown to Anthon.