You likely have some stray frames of video floating out beyond the end of your movie.
To find them, press the \ key (above the Enter key) to show your entire movie on the timeline. In your case, you will see your movie plus the additional 10 minutes of blank space beyond it.
Click, hold and drag your mouse over the blank area beyond the end of your movie and then press Delete on your keyboard.
If you've snagged all those stray frames, when you press the \ key again, your movie should fill the timeline and you'll be good to go.
I pressed the / key and it showed me my whole video and it didn't look any different or show anything further down the timeline. My scroll bar physically won't let me scroll past the end of my video (3minutes 25seconds) yet when I go to export it the preview shows me it is going to over 11 minutes with pure blackness.
Could it be something else other than stray frames if I can't physically get further on my timeline?
Thanks for your help so far,
Please post screendump of entire timeline
and export settings.
I agree with Ann. Press the \ key and then take a screen capture of your timeline and post it to this forum.