KUL > PVG > LAX

Looking to book a flight from Shanghai to Los Angeles and would like to use the full extent of the 144 hour transit free. I would be coming originally from Denpasar with a layover in Kuala Lumpur and transitting in Shanghai. The flight arrives in Shanghai 4:45am April 3, would this mean the visa does not start until 00:00 April 4 next day? If so, I can stay until 23:59 April 9, correct? Also if I have the flight booked but do not have an assigned seat yet is that ok?