Beijing 74 hour transit

I will be flying from Ho chi Min City to Beijing to Sandiego so I know I would be qualified for the 72 hour transit free transit. However, since ecery airport has different rules about when that 72 hours actually starts I have a question.
I will arrive on Jan 25 at 11:30am and leave from Beijing on Jan 28 at 1:40pm. Would I still qualify for this transit visa? Does Beinjing start the timer on arrival or from the first midnight like Shanghai does? Thanks!!