The numbers are important indicators of the subject matter of a rongorongo text. The cycles of moon and sun are similar: darkness, new light, waxing light, maximum light, turning around, waning light, last light, darkness.

Therefore the glyphs easily distinguish between these phases. But whether the subject matter is moon, sun or something else (the life cycle of some other 'person') is harder to determine. Counting saves the situation. We have earlier seen how the system works:

moon
Ca8-27 Ca8-28 Ca8-29 Ca9-1 Ca9-2
Ga2-27 Ga2-28 Ga2-29 Ga3-1
Ka3-15 Ka3-16 Ka3-17
sun
Ca5-17 Ca5-18 Ca5-19 Ca5-20
Eb3-20 Eb3-21 Eb3-22 Eb3-23 Eb3-24

28 is the number of moonlit nights in a month, 15 is the night when moon is full. 18 is the number of decades (10) in a 'year'.

G and K tell about the moon in the 1st period of the calendrical year - 29 and 16 point at the dark new moon phase respectively the end of waxing moon - while in E the parallel glyphs do not 'mention' the moon. But in E we see the 7th period, not the 1st period of the calendar. Probably moon is important in the 1st period of a calendar.

Similarities in form between the glyphs tell about similarities in meaning. In Ga3-1 the top middle part is similar to the top middle part in Ca5-20. Both glyphs presumably tell about a new light.

Ka3-17 (which, we can conclude, informs about the new moon light) is designed similar to Eb7-6, which we know means the moon.