The exports are not mangled, you can clearly see the unmangled name in the dumpbin.exe output. You also see the mangled name. That's dumpbin.exe being a bit too helpful, perhaps, it also reads the .pdb file to find the actual name of the function. It displays it on the right-hand side of the =
Simply delete the .pdb file and run dumpbin.exe again to see the difference.
You don't have a problem, it worked.