user: Question: What is the lowest number of touchdowns for left halfback willie heston who has more than 15 points?
Columns: ['Player', 'Position', 'Starter', 'Touchdowns', 'Extra points', 'Field goals', 'Points']
Types: ['text', 'text', 'text', 'real', 'real', 'real', 'real']
Sample row: ['Tom Hammond', 'Fullback', 'yes', 5.0, 10.0, 0.0, 35.0]
SQL:

assistant: SELECT MIN("Touchdowns") FROM "Table" WHERE "Position" = 'left halfback' AND "Player" = 'willie heston' AND "Points" > 15.0;