"Double surname Shangguan" means: (my) surname is a compound surname of two characters, and the surname is "Shangguan".
Chinese surnames are divided into two categories: single surnames and compound surnames. Single surname (dān xìng): a surname with only one character. As opposed to compound surnames. For example: "Li, Wang, Zhang, Liu, Chen, Yang, Huang, Zhao, Zhou, Wu, Xu, Sun, Ma, Hu, Zhu, Guo, He, Luo, Gao, Lin.
According to statistics, there are 6931 single surnames in China. Compound surnames (fū xìng) refer to surnames composed of two or more Chinese characters, such as Ouyang, Sima, Shangguan, and Ximen. Occupation, etc., and some are derived from surname changes by ethnic minorities.
The "Dictionary of Chinese Surnames" shows that there are 4,329 two-character surnames, 1,615 three-character surnames, and 569 four-character surnames recorded in Chinese characters by various ethnic groups in ancient and modern China. There are 96 five-character surnames, 22 six-character surnames, 7 seven-character surnames, 3 eight-character surnames, 7 nine-character surnames (for example: Wu Muyun from Cuanhan Shan Temple), and 1 cross surname (i.e.: Huerchuan Zhamusutal only has more).