user: Question: Name the total number of goal difference when the position is more than 20
Columns: ['Position', 'Club', 'Played', 'Points', 'Wins', 'Draws', 'Losses', 'Goals for', 'Goals against', 'Goal Difference']
Types: ['real', 'text', 'real', 'text', 'real', 'real', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'CD Málaga', 38.0, '54+16', 22.0, 10.0, 6.0, 74.0, 39.0, 35.0]
SQL:

assistant: SELECT SUM("Goal Difference") FROM "Table" WHERE "Position" > 20.0;