How many different production codes are there for the episode with 4.69 million US viewers?
CREATE TABLE table_28688 (
    "No. in series" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real,
    "U.S. viewers (millions)" text
)
SELECT COUNT("Production code") FROM table_28688 WHERE "U.S. viewers (millions)" = '4.69'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many different production codes are there for the episode with 4.69 million US viewers? ### Input: CREATE TABLE table_28688 (
    "No. in series" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real,
    "U.S. viewers (millions)" text
) ### Response: SELECT COUNT("Production code") FROM table_28688 WHERE "U.S. viewers (millions)" = '4.69'