Hi hi silent reader here!
Thanks for the news article regarding the extension of episodes to 20.
The original link is here: http://isplus.live.joins.com/news/article/article.asp?total_id=23228018&cloc=
It is said that the production team decided to extend by 4 ep even before the 1st ep was even aired. They found the story to be really good even though the script was only at episode 7 at that time.
Despite being worried for the 1% rating for ep 1, as the ratings grew from ep 2 onwards, they are filming the drama with a "hwaiting" energy.