Why does the serial number programmed on the computer change when it comes to the square dance stereo?

I also encountered this problem, I am a ballroom dancing enthusiast, at first I thought it was according to the name of the dance song the first HanZi pinyin alphabetical order, or the English order, or the number of the order, confirmed that none of them are, and later found that it is according to the each song copied into the USB flash drive in the order of playback, remember to format the USB flash drive first oh. It is also possible that the speaker playback settings will be different for different manufacturers