user: Question: What is the lowest Goal Difference, when Position is "7", and when Played is greater than 30?
Columns: ['Position', 'Club', 'Played', 'Points', 'Wins', 'Draws', 'Losses', 'Goals for', 'Goals against', 'Goal Difference']
Types: ['real', 'text', 'real', 'real', 'real', 'real', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'Real Valladolid', 30.0, 40.0, 19.0, 2.0, 9.0, 70.0, 38.0, 32.0]
SQL:

assistant: SELECT MIN("Goal Difference") FROM "Table" WHERE "Position" = 7.0 AND "Played" > 30.0;