If you actually read the article,

Of those aircraft, the ministry said 10 had either crossed the median line of the Taiwan Strait, which previously served as an unofficial barrier between the two sides, or entered the southwestern part of Taiwan's air defence identification zone, or ADIZ.

you would find that 10 aircrafts either crossed the median line of the Taiwan Strait or entered the southwestern part of the ADIZ. Neither of those is "flying over mainland China."