If each run of ruby characters representing the reading of a given base ideographic character (cl-19) participating in a kanji compound word is less than or equal to two, attach each ruby text to the corresponding base ideographic character (cl-19) (see Fig. F.1).
https://w3c.github.io/jlreq/#principles_of_jukugoruby_distribution_1
Fig. F.1 should probably be Figure 319 in the English text.