"Chinese Taipei" is something I've only seen in publications that want to placate mainland China. It's obvious Taiwan isn't China (well, not the China people usually refer to anyway) but when you call Taiwan a country, Chinese officials (and sometimes nationalist citizens) get real fussy about it.
Strangely enough, I can't find mainland China in these results, so I'm not sure why Taiwan isn't being called by its normal name here. Hong Kong and Macau do participate, though, so perhaps China still needed to be placated because of that. Taiwan getting better results across the board probably also doesn't help.
I assume they mean Taiwan?
Hong Kong is listed as a separate country, but China is not on the list.
Is China also playing dark on this TIMSS test (similar to Top500)?