changing flight in Shangai for Xiamen

I have a muti-destinations Paris to Fukuoka return ticket from Paris to Shangai, and to Xiamen by domestic flight, leaving from Xiamen 3 days later, then to Fukuoka (japan). My return from Fukuoka will be without stopover in Shangai. Is the 72hours visa time of my arrival in Xiamen start from Shangai or from Xiamen as the flight from Shangai will be on a domestic flight? (I am a french man)
Thank you for your answer.