user: Question: What is the average Grid, when Rider is shinya nakano, and when Laps is less than 21?
Columns: ['Rider', 'Manufacturer', 'Laps', 'Time', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Valentino Rossi', 'Yamaha', 21.0, '43:06.007', 2.0]
SQL:

assistant: SELECT AVG("Grid") FROM "Table" WHERE "Rider" = 'shinya nakano' AND "Laps" < 21.0;