user: Question: What is the average grid for Johnny Herbert with a Time/Retired of +1 lap?
Columns: ['Driver', 'Constructor', 'Laps', 'Time/Retired', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Mika Häkkinen', 'McLaren - Mercedes', 71.0, '1:30:44.086', 3.0]
SQL:

assistant: SELECT AVG("Grid") FROM "Table" WHERE "Time/Retired" = '+1 lap' AND "Driver" = 'Johnny Herbert';