[Freesurfer] Qdec area measure

Hi, In Qdec, what exactly does the area option measure? As I understand, qdec does its calculations vertex by vertex, which makes sense in case of cortical thickness. But if area refers to surface area how does that change from vertex to vertex? Or is it calculating the area by ROI? Is my understanding of this correct?

Also, as regards to the volume option, I was told that it is not working. But when I ran it it seems to work fine. Should I take that to mean that the calculation has bugs and that the results it displays are incorrect? Or has it been fixed?

I greatly appreciate any help in this matter.

Thank you, Devdutta