user: Question: What is the highest Laps Led with a grid of less than 4 and a finishing position of 15?
Columns: ['Fin. Pos', 'Car No.', 'Driver', 'Team', 'Laps', 'Time/Retired', 'Grid', 'Laps Led', 'Points']
Types: ['real', 'real', 'text', 'text', 'real', 'text', 'real', 'real', 'text']
Sample row: [1.0, 10.0, 'Dan Wheldon', 'Target Chip Ganassi', 200.0, '1:36:56.0586', 4.0, 177.0, '50+3']
SQL:

assistant: SELECT MAX("Laps Led") FROM "Table" WHERE "Grid" < 4.0 AND "Fin. Pos" = 15.0;