144 HOURS VISA EXEMPTION

Hello. I am a U.S. citizen and travelling to Russia and transienting to Beijing Capital, China for144 hours. According to travelchinaguide.com you can stay up to 144 hours twov exemption. United States is one of the 53 qualified countries. Could you please tell me the answer because I m hearing different answers on this matter. Please answer me soonest. Thank you very much.