not dimension to core

[KeesW]

I want to dimension to core only and it is not working. Composite has weatherboards outside and plasterboard inside. Both are designated as linings, not core. AC includes the weatherboard lining in its dimensioning, but not the plasterboard. It should at least be consistently wrong! I attached screen shots of problem and another of the dimension settings. Any ideas?

[KeesW]

And here is the second screenshot showing dimension settings. This also my default.