user: Question: How many different series numbers are there for the episode seen by 7.84 million people in the US?
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '"Pilot"', 'Ron Hughart', 'Seth MacFarlane , Mike Barker & Matt Weitzman', 'February 6, 2005', '1AJN01', '15.10']
SQL:

assistant: SELECT COUNT("No. in series") FROM "Table" WHERE "U.S. viewers (millions)" = '7.84';