Cases in Hubei is likely under reported, but this is probably more attributed to early test kit shortages and the fact to ramp up test requires time, etc. We have see the same thing in Italy and other European countries as well, the capacity is limited and testing itself is biased not aiming for coverage.

But what China's data can tell, is that there is a strategy out there to contain the virus, if implemented. And it takes about 2 months of total lockdown. It is probably the most effective containment in human history, but with a cost.

So the exact number of China's data isn't going to be meaningful to others, but the actions taken have implications and we should follow.