What CMS and player version are you using?
Total duration of the layout is displayed on Layouts page and in layout designer (1.8 series)
If you have several items in the same region, each with 30s duration, then that can easily add up to 4 mins, perhaps the following topic would be helpful as well Understanding Media Duration and how it affects the playback of a Layout
If you do not see why it stays on screen for longer than expected, you can export your layout and send to me via private message.