If these 20 glyphs should correspond to 20 periods with 18 days in each, then we can count 20 * 18 = 360 = 8 * 18 + 12 * 18 = (72 + 72) + (108 + 108) = 144 + 216.

'Etoru kiori' will then presumably represent the 3 periods of Spring Sun (and 3 * 18 = 54). Confirmation of a sort is given by Ca6-9 where 6 * 9 = 54.

If a new year comes with Ca6-1 (which is suggested by the twin mata on hau tea), then Spring Sun will end after 10 * 18 = 180 days:

From new year (Ca6-1) the calendar will stretch for 16 * 18 = 288 = 4 * 72 days, because the first 72 days (at the end of the preceding glyph line) evidently belong to the old year. At hau tea without mata the old year is ending:

Ca5-32	Ca5-33	Ca5-34	Ca5-35 (72)

I believe this interpretation of the 20 glyphs was in the mind of the creator of Mamari. The 'Moon season' (8 periods) is divided in the middle by the birth of a new year. Spring has 10 periods ending in high summer, while autumn at first sight appears to be shorter. Yet, if we add the first 4 periods of the 'Moon season' (before the arrival of new year) autumn is seen to be also 10 periods long.

The main break in time comes after day number 16 * 18 = 288 (= 180 + 108), when the 'Moon season' is beginning (cfr ragi in Ca5-32) and Sun is 'hidden' (Ca5-33--34).

288 can be interpreted as 28 (the number of nights in a month when Moon is potentially illuminated by the light from Sun) combined with 8 (the perfect number for a cycle). And then, with 28 * 8  = 224 it is easy to see how 224 + 72 = 296 can be read as 10 * 29½ plus 'one more'. The thought pattern is the same as in 365 = 364 (= 14 * 26) + 1:

With a little twist a pair of other important numbers will appear: