Hi Barry,
The List Schemes (and entire old Calculation engine) have not been improved upon since ArchiCAD 6.5 to my knowledge, so it is not surprising that they do not 'know' about solid element operations. It's wrong / bug of course - but whether GS will ever improve the engine and the clunky interface seems doubtful, even though this is essential to many people.
The element schedules may show the correct result here, for wall surface, but there are other cases where they do not show the proper result of a solid element operation. My experience is verify before trusting in all things schedule related...
Best,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB