user: Question: How many teams have 21 tries for?
Columns: ['Club', 'Played', 'Won', 'Drawn', 'Lost', 'Points for', 'Points against', 'Points difference', 'Tries For', 'Tries Against', 'Try Bonus', 'Losing Bonus', 'Points']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Club', 'Played', 'Won', 'Drawn', 'Lost', 'Points for', 'Points against', 'Points difference', 'Tries For', 'Tries Against', 'Try Bonus', 'Losing Bonus', 'Points']
SQL:

assistant: SELECT COUNT("Points difference") FROM "Table" WHERE "Tries For" = '21';