CREATE TABLE table_18728 ("#" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "Production code" CLOB, "U.S. viewers  ( millions ) " CLOB)

How many different original air dates did the episode number 6 have?
SELECT COUNT("Original air date") FROM table_18728 WHERE "#" = '6'
SELECT COUNT("Original air date") FROM "table_18728" WHERE "#" = '6'