Playlists with #EXTVLCOPT:start/stop-time don't show duration correctly

Hi,

So I have a video in my .m3u playlist like:-

#EXTINF:1640,Some video lasting 3h but I'm only playing 27m20s worth
#EXTVLCOPT:start-time=0
#EXTVLCOPT:stop-time=1640
../media/fred.mp3

but when I look at the list in the main window I see the 3h full length of fred.mp3, not 1640 seconds worth that I've put in the playlist. The video plays 27m20s correctly but the duration column in the main window and the total length of the playlist are wrong due to using the full length of fred.mp3

I've tried setting the #EXTINF setting to include the length but that's ignored too.

It's very confusing as I need it to be accurate to the second as my playlist is 12hrs long and I need certain videos to play at certain times throughout.