Hemisphere differences in cluster size

I am working on a surface-based analysis. I followed the example 8 from AFNI proc.py, and have used 3dttest++ on the results. I would like to perform a cluster correction for this data. I ran slow_surf_clustsim.py but got vastly different cluster sizes per hemisphere (1071 for the left hemisphere and 249 for the right). Given my understanding of slow_surf_clustsim this doesn’t make any sense to me. I am wondering if this kind of discrepancy is normal?

My script:

for hemi in lh rh
slow_surf_clustsim.py -save_script 1_2_clustsim_${hemi}.sh
-on_surface yes
-uvar blur 4.0
-uvar niter 1000
-uvar spec_file suma_MNI_N27/std.141.MNI_N27_${hemi}.spec
-uvar surf_vol suma_MNI_N27/MNI_N27_SurfVol.nii
-uvar pthr_list 0.05 0.01
-uvar results_dir …/surf_${hemi}
-verb 1