CREATE TABLE table_21584646_10 (week_of VARCHAR, champion VARCHAR)

How many weeks are shown for the champion of john mcenroe 6 2, 6 3?
SELECT COUNT(week_of) FROM table_21584646_10 WHERE champion = "John McEnroe 6–2, 6–3"
SELECT COUNT("week_of") FROM "table_21584646_10" WHERE "John McEnroe 6–2, 6–3" = "champion"