user: Question: How many rating/share values does the episode aired on Saturday, May 9, 2009?
Columns: ['Episode #', 'US air date', 'Rating', 'Share', 'Rating/Share (18–49)', 'Viewers (millions)']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Thursday, April 9, 2009', '6.5', '11', '2.6/8', '10.21']
SQL:

assistant: SELECT COUNT("Rating/Share (18–49)") FROM "Table" WHERE "US air date" = 'Saturday, May 9, 2009';