CREATE TABLE table_56492 ("Driver" TEXT, "Constructor" TEXT, "Laps" FLOAT, "Time/Retired" TEXT, "Grid" FLOAT)

what is the sum of laps when grid is less than 20 and johnny herbert is driving?
SELECT SUM("Laps") FROM table_56492 WHERE "Grid" < '20' AND "Driver" = 'johnny herbert'
SELECT SUM("Laps") FROM "table_56492" WHERE "Driver" = 'johnny herbert' AND "Grid" < '20'