Mean Velocity or Deformation Range

My case study is on 38 TSX images, After completing the steps stamps(1,7), the mean velocity plotted using ps_plot(‘v’-1) in MATLAB gives me the range of deformation between -2 mm/yr to +3 mm/yr but the cross references using other methods give the mean velocity between -25 mm/yr to +25 mm/yr. Is there any way to address this problem with StaMPS or Am I missing something?