Autodesk has added a knowledge network article, for those that superimpose profiles in Civil 3D, and the profiles appear to be shortened and do not match the 0+00 limit of the profile view, This is a known issue, and Autodesk has created a workaround for this problem.  Please see the link to the article below. 

https://knowledge.autodesk.com/support/autocad-civil-3d/troubleshooting/caas/sfdcarticles/sfdcarticles/SuperImposed-profile-not-extending-correct-limits.html

If you have any questions or comments, please reply to this post, or email me at [email protected]