SEA>PVG>HKG then return trip HKG>PEK (layover)>SEA

Hello,

I think we are eligible to travel to China without a Visa, but I want to be sure I'm understanding the rules correctly. We are flying from Seattle to Shanghai for 5 days (less than 144 hours) and then Shanghai to Hong Kong. I believe I'm correct that we are eligible for the 144-hour exemption for this leg of our trip.

After 6 days in Hong Kong we will be flying from Hong Kong to Beijing where we have a 5-hour layover before continuing on to Seattle. For this trip home from Hong Kong can we use the 24-hour TWOV or is there a problem that we have a layover in mainland China after using the 144-hour exemption the previous week?

Do we treat our SEA>PVG>HKG and HKG>PEK (layover)>SEA as two different trips? I just want to be sure that doing a layover in mainland China on our way home doesn't complicate our Visa-free travel plans.

Thank you so much for any guidance.