I guess one way to answer the question is to say that the bluemarked signs together illustrate the shape of a crescent, and Moon should not be up in the 'sky' but down in the 'water'. 'Fire' (Sun) on the other hand cannot be down in the water. Therefore the zodiac has been created to resemble a great canoe (the bluemarked signs) containing the 'sky' ('fire').

The blackmarked signs delineate a circle and it can be imagined as a great sail (raa). It would in other words be the same idea as in this petroglyph from Easter Island (in Heyerdahl 3):

According to the current situation the blackmarked Aquarius, Capricorn, Sagittarius, Scorpio, and also Libra, have been forced below the sky equator (the 'water line'). This is another argument for not needing any more bluemarked extra signs in winter (north of the equator) - these zodiacal signs are already 'down in the blue'.

We can therefore understand that the 4 blackmarked Aquarius - Scorpius should be counted together with the 12 blue signs, and the result is 16 'water signs' (= 472 / 29.5). Maybe the text of G consists of a description of 16 'water signs' (periods dictated by the Moon). On Easter Islands they must have been aware of their position and of the corresponding location on the sky dome.

Libra is 'inside the Moon canoe', and below it is the first of the blue figures (with a fool's cap) at the beginning of the 12-sign sequence. On the other hand this is counterbalanced by the last of the blue signs (the circle with a 'baby hippopotamus' inside) coming immediately after Pisces. I think the last of the blue signs is the lower of the 2 fishes, and that the blue circle touching it belongs to the sign, just as the circle around Harpocrates touches Libra and belongs to the sign. The upper fish, on the other hand, is not touching the circle with the Sun eye (wedjat) - because that way it becomes a sign for separation, showing how sky now is rising above the earth.