As of last year about 12,000 mines - they are trying to close smaller mines which are often illegal and have high death rates. However, they are still expanding capacity [2] - so the closure of mines isn't a good proxy to production of coal.
Putting the 13 million metric tons cut into context - China produced 3 billion and change from 2010-2014 [2]. So, while it might be important for Beijing and may signal a change of stance (?), from a China usage perspective it isn't a big difference, by itself.