Ashenhurt and other sett charts tell you the setts for balanced weaves–where both the warp and the weft show equally. Weavers often don’t want both to show equally, they may want the warp to predominate in some cases, or the weft. Then you adjust the sett from the charts accordingly–more warps per inch (epi) for a warp predominate fabric or fewer epi for a weft predominate cloth. Read more in my new book, Weaving for Beginners, in the chapter on sett. These photos are found on page 277.