Beijing free transit visa for 72 hours

Hello, I have tickets to Being with one stop (2h.10 min) through changshui Intl. and then arriving to Beijing on the 3rd. Of December at 00:50. My flight back from Beijing to Kuala Lumpur on the 6th of December at 2:30 am.
Am I still fitting into free transit conditions? If to count from schedule to schedule then it’s 73,5 hours .Maybe I can arrive to airport way earlier for flight to KL and then cross security few hours earlier? Or it doesn’t work like this?

Thank you Very much for your quick respond.

Lina