There are three descriptive lines:
 All voxels ("VOI")
 All non-zero voxels ("VOI <>0")
 All voxels with positive intensity ("VOI >0")

For each, you get the number of voxels (nvox), cubic centimeters (cc), minimum (min), mean (mean) and maximum (max) and standard deviation (SD) for the voxel intensities under the drawing...

Overlay /Users/chris/src/NiiStat/roi/AICHA.nii
Center of mass XYZ 90.35x108.06x87.24
VOI nvox(cc)=min/mean/max=SD: 1153456 1153.46 =8.0000 88.3904 184.0000 = 19.5849
VOI <>0 nvox(cc)=min/mean/max=SD: 1153456 1153.46 =8.0000 88.3904 184.0000 = 19.5849
VOI >0 nvox(cc)=min/mean/max=SD: 1153456 1153.46 =8.0000 88.3904 184.0000 = 19.5849
Mode: 86.00146484375