I am Australian passport holder. Staying 70.5 hrs.

I am arriving into Shanghai (PVG) airport at 18:30 on July 29th and leaving again on Aug 1 at 16:15. I overlooked organising a visa and am relieved to find there is a 72-he visa free period. I am visiting a factory in Suzhou. Can I take advantage of the 72- hr period? If so, what do I do? Just arrive at PVG and explain why I am 'visa-less'? I depart soon and so am hoping you can confirm this asap. I will sleep better. I am so worried.
Thanks