CREATE TABLE table_204_868 (id DECIMAL, "outcome" TEXT, "no." DECIMAL, "date" TEXT, "tournament" TEXT, "surface" TEXT, "opponent" TEXT, "score" TEXT)

tell me the number of matches played on clay .
SELECT COUNT(*) FROM table_204_868 WHERE "surface" = 'clay'
SELECT COUNT(*) FROM "table_204_868" WHERE "surface" = 'clay'