CREATE TABLE table_6402 ("Result" TEXT, "Date" TEXT, "Race" TEXT, "Venue" TEXT, "Group" TEXT, "Distance" TEXT, "Weight  ( kg ) " FLOAT, "Time" TEXT, "Jockey" TEXT, "Winner/2nd" TEXT)

What was the combined weight in kilograms of the horses in the race at Chelmsford stakes?
SELECT COUNT("Weight (kg)") FROM table_6402 WHERE "Race" = 'chelmsford stakes'
SELECT COUNT("Weight (kg)") FROM "table_6402" WHERE "Race" = 'chelmsford stakes'