CREATE TABLE table_72937 ("Season" TEXT, "Date Released" TEXT, "# Of Episodes" FLOAT, "# Of Discs" FLOAT, "Special Features" TEXT)

How many discs for the complete 4th series?
SELECT MAX("# Of Discs") FROM table_72937 WHERE "Season" = 'The Complete 4th Series'
SELECT MAX("# Of Discs") FROM "table_72937" WHERE "Season" = 'The Complete 4th Series'