In positions area of video marker you can see
| · | Actual time and frame in preview of selected file.
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| · | Begin time and frame (In point) says, where selected file starts in output (joined) file.
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| · | End time and frame (Out point) says, where selected file ends in output (joined) file.
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Also you can save new In point
and Out point 
to select only part of selected file as well as you can Reset In and Out points 
to select whole selected file.
Cutting video stream will cut audio stream of this file to same duration.
By changing In point or Out point you may see selected part of the file at track bar
below.
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| · | White area is a part of video stream between Begin and End (In point and Out point).
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| · | Red area (parts before In point and after Out point) will be ignored in output.
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