Its basic meaning should be a negative of the 'red cloth', for instance that the season of the sun is ending. The kai gesture should mean that the 'black cloth' is increasing its power. The period number (20) suggests a limit has been reached, and the straight vertical line at left in Ga5-27 also indicates a limit.

We have, furthermore, evidence that the apex of the sun just has passed away (cfr the excursion at maitaki):

If sun has 300 days, then Ga5-27 will be located as day number 152 and presumably be meant to determine the character of the preceding henua. Likewise ariki at Ga5-24 could determine the character of henua in Ga5-23 (equal to the preceding season).

The fat honu in Ga5-25 seems to be a further determinant of henua in Ga5-23, to be contrasted with the leaner honu in Ga5-28. When sun declines also growth declines. The change comes with Ga5-26.