In Hong Kong and Macau, 1 fen = 1⁄10 mu = 76.14 square meters = 91.06 square yards.
[5]
In Taiwan and Japan, 1 fen = 1⁄10 jia = 969.92 square meters = 10,440 square feets.
[6]
Taiwan used to be ruled by Holand and then by Japan. Its measurement system was influenced by these two countries. And 1 fen has been set to be 1/10 of a Jia instead of a mu. [6]
One mu and three fen of land, or 1.3 mu of land (simplified Chinese: 一亩三分地; traditional Chinese: 一畝三分地; pinyin: yī mǔ sān fēn dì) is a Chinese idiom that figuratively refers to someone's small personal domain or limited territory, often implying a narrow scope of influence or control.[7][8]
^"權度法 [Quándù Fǎ]", 政府公報 [Zhèngfǔ Gōngbào, Government Gazette], vol. 957, Beijing: Office of the President, 7 January 1915, pp. 85–94[permanent dead link]. (in Chinese)