See all the CAD experts here and many still using old versions, I need help getting rid of this error or do I just ignore it? Using Carlson 2014 with C3D 2010.

I started the drawing in my software, then I was playing with BriCAD to check it out and now I get this message. I tried TrueView to save back to my version and this is the message I get now. Help ME!
I get that message whenever I open a Cad drawing that has been saved down to a lower version. I ignore it and I have not noticed anything detrimental to the drawing.
What is in the drawing? Points, lines, surfaces?
Topo or boundary?
Is there a BAK of your old file?
It really depends on the functionality you need from the drawing.
People need to use the export command instead; then that doesn't happen.