Tagata in Gb6-17 has his fist held high in front:

Gb6-17 (0)

The normal way of holding an object is with the right hand. But the man in Gb6-17 is looking at us and therefore it must be his left fist which is held high.

However, in the rongorongo system (and presumable all over the world once upon a time) the left side is the back side. The front side is the facial side, the right side, the side in light.

The dilemma is easily solved: A text is a mirror of reality. Tagata in Gb6-17 is depicted as if in a mirror. Therefore it is his right fist which is held high, right and front must be on the same side.

The mirror of reality idea implies a text is not the true reality. The idea can be extended to cover also time. In the physical universe objects fall downwards due to gravitation. But growing things move upwards. The animate world is a mirror image of the inanimate world.

The rongorongo texts undulate upwards on the tablets. They are only descriptions of reality. These descriptions move to the right, but in reality events pass away to the back side. Life moves forward but history in the other direction, down through time.