Don’t worry, Sophie. There is no problem. Your itinerary is definitely eligible for 240 hour visa free transit and you can proceed with your travel plans with absolute peace of mind. The immediate points before and after mainland China are in two different countries/eligible territories (Malaysia and Macau) and your total stay within mainland China is less than 240 hours. So, at the time of your check in in Kuala Lumpur you will declare that you will travel to Macau via China using 240 hour visa free transit and you will present your Beijing to Macau flight ticket. Also, upon your landing in Nanjing the first thing that you will do will be to approach 24/240 hour visa free transit where you will apply for a temporary entry permit by presenting your flight ticket to Macau and also your short itinerary. After the permit is granted, you will head to the immigration and then outside the airport to enjoy your time on your own. Have a nice trip!