MND = Ministry of National Defense

PLA jets = any Chinese military aircraft the MND views as counting

ADIZ = Air Defense Identification Zone

Note that this question refers to aircraft entering the ADIZ; the MND reports both this number as well as the number that fly close to the ADIZ whether or not the subsequently enter it

In the event of any lack of clarity, this question will resolve to the number given in the MND's tweet pertaining to May 20th, even if that tweet appears to conflict with the conditions in this question.

If the MND does not tweet about this, any other form of official statement may be used. If no official statements are available, resolves to Unknown

https://twitter.com/MoNDefense

Resolves on May 21st, as the MND usually announces the day after.

Note that on days of unusual activity they often release a preliminary incomplete count on the day itself.