user: Question: How many different end dates are there for the series seen by 4.2 million people?
Columns: ['Series', 'Start date', 'End date', 'Episodes', 'Average viewers (millions)']
Types: ['real', 'text', 'text', 'real', 'text']
Sample row: [1.0, '22 August 2009', '3 October 2009', 7.0, '5.09']
SQL:

assistant: SELECT COUNT("End date") FROM "Table" WHERE "Average viewers (millions)" = '4.2';