user: Question: When Yidu 宜都 is the commandery what is the lowest number of countries?
Columns: ['Province', 'Provincial capital', 'Commandery', 'Commandery capital', 'No. of counties']
Types: ['text', 'text', 'text', 'text', 'real']
Sample row: ['Yang 揚', 'Jianye 建業', 'Danyang 丹陽', 'Jianye 建業', 16.0]
SQL:

assistant: SELECT MIN("No. of counties") FROM "Table" WHERE "Commandery" = 'Yidu 宜都';