How many series numbers do the episodes originally aired on October 28, 1990?
CREATE TABLE table_2226817_6 (
    no_in_series VARCHAR,
    original_air_date VARCHAR
)
SELECT COUNT(no_in_series) FROM table_2226817_6 WHERE original_air_date = "October 28, 1990"
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 series numbers do the episodes originally aired on October 28, 1990? ### Input: CREATE TABLE table_2226817_6 (
    no_in_series VARCHAR,
    original_air_date VARCHAR
) ### Response: SELECT COUNT(no_in_series) FROM table_2226817_6 WHERE original_air_date = "October 28, 1990"