CREATE TABLE table_17920 ("Position" FLOAT, "Club" CLOB, "Played" FLOAT, "Won" FLOAT, "Drawn" FLOAT, "Lost" FLOAT, "Pts For" FLOAT, "Pts Agst" FLOAT, "B.P." FLOAT, "Points" FLOAT)

What is the number of played when points against 645?
SELECT COUNT("Played") FROM table_17920 WHERE "Pts Agst" = '645'
SELECT COUNT("Played") FROM "table_17920" WHERE "Pts Agst" = '645'