Hong Kong and Macau are weird in that they're part of China but have a different government and separate economic system. They're both former European colonies that were "given" back relatively recently. I don't see the main part of China on the graph, but maybe I just missed it.

Here is the source: https://www.oecd-ilibrary.org/education/pisa-2022-results-volume-i_53f23881-en

For the asterisk:

• Caution is required when interpreting estimates because one or more PISA sampling standards were not met (see Reader’s Guide, Annexes A2 and A4). Long-term trends are reported for the longest available period since PISA 2003 for mathematics, PISA 2000 for reading and PISA 2006 for science. The OECD average does not include Costa Rica and Spain for short-term change in performance.

I'm looking for China, IIRC they only allowed Hong Kong and Macao to participate, the rest of China did not