15 days Visa Free in China

A group of 10 of us from Malaysia are going to China this coming November under 15 days visa free option. After 12 days, we arrive in Shanghai to take a Royal Caribbean Cruise at Shanghai Wusongkou International Cruise Terminal for 5N6D to Japan. We will disembark in Shanghai again after 5 nights. l would like to confirm when we join the cruise, it is considered as exit China and when we are back to Shanghai again after 5 nights, we are entering China again and a new 15 days visa free applied. Am l right? If not, are we qualified for the 144 hours visa free criteria? Thank you.