The solfege chart and hand signs on page 1 are helpful visuals for learners, but it is not a complete chart. It leaves out some of the sharp hand signs on the right side picture like Li (#6). It's there as a guide, especially if you have anyone younger that has grown up in middle school or high school choir that used the solfege or number system. They will see the correlation. Even if you choose not to use it, the pitch ladder of space between notes/steps/intervals does create a kinesthetic reminder to the distance between intervals that can make for more accurate singing, especially with skips & leaps.