Consider the slight difference between this pair of glyphs and what can be found in the moon calendar of Mamari:

Da3-105 Sb2-11
2 4 (?)
Ca7-19 Ca8-6
4th period 6th period

The difference 6 - 4 = 2 agrees with the difference 4 (?) - 2 = 2. The little Moon in Ca8-6 is imperceptibly more bent that that in Ca7-19, isn't it?

Should this then make us change the period numbers from 4th / 6th into 2nd / 4th?