afni.nimh.nih.gov

I use the 3dtttest++ as followed:
3dttest++ -setA /subject1/1.niml.dset \
/subject2/1.niml.dset \
.
.
.
-setB /subject3//1.niml.dset \
/subject4//1.niml.dset \
.
.
.
-prefix 3dttest.niml.dset
And I get the WARNING: Duplicate labels for datasets in option '-setA'"
WARNING: Duplicate labels for datasets in option '-setB'"
Does it do some effect on the result of the 3dttest.niml.dset? How can I solve it? Change the name of the subject?