TL;DR: gaining national master level in China is based on gaining competition norms, likely to be in the amateur league.
As you know, national federations can set their own standards for national master titles:
National chess federations are free to set whatever standards they want for such titles [e.g. National Master], which are not recognized by FIDE. Standards for "Master" titles in different countries vary, but are usually based on criteria such as achieving a certain rating (typically about 2200 Elo), achieving the required number of tournament performances ("norms") at a certain level, or featuring prominently in the country's national championship. In some cases, it may extend to honorary titles awarded to (for example) prominent chess administrators, business patrons or politicians.
Source: wikipedia, emphasis is mine.
In China, you can gain the national master title by playing in tournaments and getting NM norms;
There are really two tracks for chess players. One is run by the National Chess Association & the National Chess Academy, as well as the associated provincial- and municipal- level chess academies. They award certificates for amateur players, from level 6 (the lowest) to level 1 (the highest), which are followed by the titles of Candidate Association Master Association Master & National Master. Meanwhile, the National Sports Bureau uses a different classification system entirely (recognising instead the ‘Athlete system’), bestowing upon the elite players the titles of Third class (the lowest), Second class and First Class (the highest) Athlete, National Elite and International Elite.
Chess players gaining the required norms (gaining a certain placing in some designated tournament perhaps, or satisfying the required win rate) can apply for First Class certification. For example, I gained the titles of Association Master and First Class Athlete through competing in various events.
Source: Chess in China: Unveiling the Chinese System on Chess.com, emphasis is mine