user: Question: How many release dates does Volume 4 DVD have?
Columns: ['DVD name', 'Ep No.', 'DVD No.', 'Release date', 'Additional information']
Types: ['text', 'real', 'real', 'real', 'text']
Sample row: ['Volume 2', 13.0, 1.0, 2009.0, 'Includes the entire second Season.']
SQL:

assistant: SELECT COUNT("Release date") FROM "Table" WHERE "DVD name" = 'Volume 4';