user: Question: Name the total number of series sorted for when released is April 2010
Columns: ['#', 'Series Sorted', 'Title', 'Author', 'Doctor', 'Featuring', 'Released']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '6Y/AA', 'The Nightmare Fair', 'Graham Williams (adapted by John Ainsworth )', '6th', 'Peri , Celestial Toymaker', 'November 2009']
SQL:

assistant: SELECT COUNT("Series Sorted") FROM "Table" WHERE "Released" = 'April 2010';