unmatching song length and original track playing

Whenever I edit a song in audacity I’m always cutting parts out–so the song is and should be shorter. But when I export the file and convert it to mp3, the song still shows up as being its original length; for example, I edited a song that was around 6 minutes and got it down to around 3 minutes. When I play it in iTunes it plays as the edited version, but it still shows up as being 6 minutes in length, and when the cursor gets to the end of the edited part it jumps to the end of the 6 minutes. That wouldn’t be an issue–other than being confusing–EXCEPT that if I don’t play the song from the beginning–like if I click halfway through the song or something–it plays the original track, not the edited version!

This makes no sense to me and probably doesn’t make sense to anyone else, please ask me questions that might help clarify what I’m trying to say… is it a problem with iTunes and not with Audacity? does it have to do with Macs being dumb in general?? I don’t think I can screenshot anything that would help you understand…

Probably (I can’t think what else it might be).
I don’t use iTunes myself, but there’s a couple of bits in the Audacity manual that may help:

It could be another symptom of this iTunes bug: https://forum.audacityteam.org/t/itunes-audio-clips-truncated/42885/2