the scientists in Hong Kong are not likely mis-calculating R naught nor mis estimating the % of cases resulting in deaths. (others are though). They are doing it all properly, using case counts that take in account the time between the virus first makes its contact with the humans affected, then the time period of symptoms, and then spread to other humans. They do know the proper way to determine Rnaught, and took painstaking efforts to accurately obtain correct and verified
clinical data.
These professionals are producing these research papers in a super timely fashion, in which there is not time to be peer reviewed, which would take months longer, and make their reports useless to world health professionals trying to make decisions on how to stem the tide of this nasty virus. Its much closer to 4, than 3.0 or even 2.5, based on a lot of other data scientists around the world have been gathering on this situation. Its a rapidly evolving situation which requires these types of assessments to be done, and then variances assigned to certain parameters.
You can learn more about it here if you desire....
Its still tracking as an geometric increase, well above Rnaught of 2.5, or even 3.0... (the numbers presented above post on the case increases, even if they are still way too low versus actual, are confirming the geometric spread - exponential when plotted on log charts - increases shown in this video below)
And if you dont believe the above maybe a Dr who is professor of medicine and infectious diseases from Mayo Clinic, saying "we are basically seeing a Pandemic" - would provide some measure of credibility to the seriousness of what is going on... and most importantly he says the cases being counted right now, are
absolutely an underestimate. (I.e. the now 20,000, is way low)