glyphs
glyph labels	Sb2-11	Sb2-17	Sb2-20	Sb2-23
'period' nos.	6	8	9	10
descriptions	'moon'	'oval'	'bent oval with mark'	'bent oval without mark'
number values	4 (?)	6	7 (?)	8 (?)

These four glyphs are alike, with the exception of the signs on top of the left wings. I imagine these signs might be number values. The value 6 is reasonable e.g. according to a glyph sequence in Échancrée, the rest are 'educated' guesses.

But in the moon calendar of Mamari there is some support for my view.

I should now rewrite from 12 to 10 months in the Keiti calendar of the year.