Flaw of the time streaming

I noticed that some track that I run in my Playlist have shorter time running time in statsfm, although I played it full. Like example the song is 2:45 but in the app it's recorded sometime 2:30+ but also sometime run less than a minutes like 1:10. I also noticed that it seem to run timer way faster. Like example the song is played at 10s but in the app it show like 15s as example, showing flaw