Sort order in Playing window

[hapx]

Hello,

After entering a directory (folder) containing my mp3, in Playing window, there is a list of mp3.
It seems OK, but in fact in my case there are 2 parts:
- first part is a list not totally sorted in in alphabetic order, and with a number (e.g. 1, 2 or 3 etc..) before
the song name.
- second part is a sorted list in alphabetic order, without any number before the song name.

My questions are:
1- What is the signification of the number before the song name?
2- Why the list is not sorted in one single part?

Thank you for your help.


Edit: I find out that the number is apparently the track number. In case of a folder for an artist with different albums, and hence different tracks, this gives kind of unsorted songs by name.

So I would like to always have alphabetic sort by song name regardless of track number.