Well, if it looks correct once you've changed the precision, I'll go ahead and close this thread. The change I mentioned for updating the display of all formatted currency values would be apart of CORE-1092.
That might explain it. However, the addition of currency precision in v3.5.1 did not include updating every location in the system that might display formatted currency values. It probably should, but that would be a different task for another version.
Blesta uses the ISO-3166-1 standard for country codes and ISO-3166-2 for subdivisions. Hong Kong does not define any standard ISO-3166-2 subdivisions, which is why none are listed.
I would suggest using my States & Countries plugin to update the entries to better suit your needs.