I think this mystery is solved now. And with this we can see that the original post on the .ash-files is flawed in many ways.
The first two numbers refer to the filetype. For example lossless .wav or .flac-files always begin with 11 (also .ogg), and lossy formats like .wma and .mp3 always begin with 10. Number 12 is for .m4a.
Then the next numbers tell how many centiseconds the song length is, and I verified this. For example my 13:37 track is 81713 centiseconds, which converts back to exactly 13.6188333 minutes, or 13 minutes and 37,129998 seconds.
And now I know where the problem of my previous post lies. It analyzes the song length possibly too accurately (or not too accurately, depending on how you look at it) which leads to the game interpreting two possible track lengths of the same song. It's a very annoying bug.