72 or 144 hours transit in Guangzhou

I see some sites say Guangzhou only allows 72 hours transit, while some say Guangzhou allows 144 hours transit (including this site). Which one is correct?
And can I stay in my transit country for only two hours? My route is USA -> Manila (2 hours) -> Guangzhou -> Singapore (after 5 days. transit for 2 hours) -> USA. Does that work?