Dubai - Beijing - Colombo

Hi, I am flying Dubai - Beijing - Colombo, and will be in Beijing for less than 72 hours, but the Beijing to Colombo flight stops at Kunming on the way out (3 hours where I won't leave the airport) - I will pass through immigration only twice, in and out in Beijing. Does this work for the 72 hours transit visa, or will the fact that I technically land in Beijing and only fly out of shanghai affect things?