The ancient people often said that the 28 stars refer to

Twenty-eight constellations were divided by ancient astronomers in China to observe the movements of the sun, the moon and the five stars. They are called Jiao, Kang, Bi, Fang, Xin, Wei, Ji, Jing, Ghost, Liu, Xing, Zhang, Yi, Bi, Kui, Lou, Stomach, Bi, Gou, Shen, Dou, Niu, Nv, Xu and Dou.

Twenty-eight constellations, an ancient astronomical term, are composed of black dragon in the east, suzaku in the south, white tiger in the west and Xuanwu in the north.