CREATE TABLE table_10007452_3 (order_year VARCHAR, fleet_series__quantity_ VARCHAR)

how many times is the fleet series (quantity) is 468-473 (6)?
SELECT COUNT(order_year) FROM table_10007452_3 WHERE fleet_series__quantity_ = "468-473 (6)"
SELECT COUNT("order_year") FROM "table_10007452_3" WHERE "468-473 (6)" = "fleet_series__quantity_"