What version of AC are you using?
In 13 the element Information palette will show both the volume and the plan area amended when a column intersects.
The schedule as you noted shows only the volume amended.
This is a bug which I believe this has come up before.
This is another example of inaccurate scheduling information. These kinds of problems prevent users from using Archicad's BIM potential when users cannot easily extrude accurate data.
Hmmph.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"