Why are the sixty-four hexagrams in Fuxi's and Fiona Fang's pictures opposite?

The reason is that this picture is drawn according to the principle of "unity of opposites of Yin and Yang", and each of the 64 hexagrams has a corresponding "wrong hexagrams" (wrong hexagrams are opposites of Yin and Yang). If sixty-four hexagrams are connected by drawing thirty-two diameters, then the two hexagrams corresponding to each diameter are wrong hexagrams, which accords with innate gossip's theory of Yin and Yang.