Hello!
This is actually a bug, that we know about.
All the background calculations in ARCHICAD are actually based on meters (whatever units you are using, the calculations are done in meters). The problem here, is that the algorithm we use to convert the results in the model and in the Interactive Schedule Add-on slightly differs, and the results after the conversion end up a fraction of a mm smaller in the Interactive Schedule, and since it seems smaller than 1', it will convert to 12" instead. The displayed value is actually correct, it is just in the wrong format.
This bug is on our to-do list, but it is deep in the code, so we are still working on a way to make it happen. I understand your frustration about this issue, sorry about the inconvenience!
Regards,
Daniel Alexander Kovacs
Professional Services Consultant
GRAPHISOFT
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