The only way to get 10 mins. from 68 mins., would be to Export/Share/Publish the 68 min. Timeline in basically 10 min. segments, that one could watch sequentially, 01, 02, etc., through 07, or to edit that Timeline much more tightly, to trim it down to 10 mins.
For ease in doing the first, you can use the WAB (Work Area Bar), to Export/Share/Publish segments of the Timeline. For more info on the WAB, see this article: http://forums.adobe.com/message/3961685#3961685
(Hunt beat me by five minutes!)
There are Work Area Bars that slide left and right above the timeline. The set a start and stop point for both real time rendering and output transcoding.
When you create a computer video file, there is a check box that says "Share WorkArea Bar Only".
Set the bars for the ten minutes you want and check the box.