Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21781578_2 ( season_no VARCHAR, us_viewers__millions_ VARCHAR )

### Question ###
What was the number of season number entries that had US Viewers of 12.30 million?

### Accurate SQL ###

SELECT COUNT(season_no) FROM table_21781578_2 WHERE us_viewers__millions_ = "12.30"