user: Question: How many people wrote the episode that had 6.34 million viewers?
Columns: ['Episode', 'Title', 'Directed by', 'Written by', 'Original airdate', 'Duration', 'Viewership']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '" Keep On Running "', 'Tony Dow', 'John Sullivan', '9September2005', '30 minutes', '8.88 million']
SQL:

assistant: SELECT COUNT("Written by") FROM "Table" WHERE "Viewership" = '6.34 million';