I read from a previous post that the "{lh,rh}.w-g.pct.stats files in $SUBJECTS_DIR/subject/stats … will have the mean gray-white contrast for each ROI in the aparc."

I've looked at the lh.w-g.pct.stats file and am not sure which values I should be looking at if I am interested in the ratio of grey to white matter averaged over each of the ROIs? What are the area in mm2 and the SNR in this w-g context?