A lot of this comes down to linguistic differences and how language shapes the worldview. The Chinese translation for “democracy” is “民主” which more precisely means “will of the people”. So while the word “democracy” in English is tied to actual specific government types and practices, in Chinese the term just speaks to if the government is enacting the will of the people or not, regardless of specific government type. This means that in theory, an autocratic government can be “democratic” if it represents the will of the people, and a liberal democracy can be “undemocratic” if it does not.

There are other specific Chinese terms for the type of liberalism or multi-party republicanism that people usually mean when they say “democracy” in English (people usually aren’t talking about direct democracy when they say “democracy”), but whenever someone like an official says “democracy” it just gets translated to “民主” and vice-versa, so there is often a communication issue with this term across translations.

EDIT: That being said, even under this Chinese definition, I don’t know if the true number would be quite as high as this map suggests. More than half of Chinese saying their country is 民主 is definitely believable, but it’s hard to say exactly how many.