user: Question: What is the lowest number in series when U.S. viewers is 0.23 million?
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'U.S. viewers (million)']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [2.0, '"Now or Never"', 'Miguel Arteta', 'Mike White', 'October17,2011', '0.19']
SQL:

assistant: SELECT MIN("No. in series") FROM "Table" WHERE "U.S. viewers (million)" = '0.23';