Without any information about how these datasets were
created, particularly regarding how you put the 2 ROI
contrasts together, it is hard to say much.
I can guess that this last clustering in the GUI finds
15 ROIs, but they are not from unique values. So
while there are 15 remaining clusters in the dataset,
there are only 12 distinct non-zero values.
In the cluster report, click on "3dclust" to generate
a 3dclust command in the terminal window, and then
cut-and-paste that command to run it. Look at the
"Mean" values for each cluster and see if there are
duplicates.
- rick