I've always kinda adjusted to this but right before I save a looped region, the segment length will read, say, "20 secs", but the resulting file will be 20 secs plus 1 or 2 frames.
I've learned to kinda adjust for this, but I wonder if it's something that can be fixed.
If you're an NTSC body it might have something to do with there not being an integer number of frames / second. Also I think the DF, NDF thing can trip you up as well.
I'm a PAL guy so I might be way of base.