NaN = Not a number, which belongs to the problem of the software itself. Either the reading failed in a few days (for example, the network card was stuck and the result was not found), or it has expired.

NaN, the abbreviation of Not a Number, is defined in IEEE floating-point arithmetic standard (IEEE 754), which represents some special numerical values (infinite and non-numeric values (NaN)) and is adopted by many CPU and floating-point operators.

in QQ 27 beta 3, QQ music monthly subscription service "Music VIP" was officially upgraded to "QQ Music Green Diamond Noble" and became a new member of QQ Diamond Noble Service. While retaining the original rights of free appointment of Qzone music and free ordering of QQ songs, Green Diamond Noble also added the right to download high-quality genuine music from QQ music player.