Thanks for the question! This has to do with a very careful reading of the last rule. It tells us that “ANY portion with eight consecutive beads must have at least one bead of each color.” So in a nine-bead strand, beads 1-8 need to have at least one bead of each color, AND beads 2-9 need to have at least one bead of each color. Because those are both 8-bead portions, and ALL (any) 8-bead portions need to have at least one of each color. If you put R in 9, you won’t be able to fit O in both 9 bead strands.
Hope this helps! Feel free to ask any other questions that you might have.
