Statistical analysis in CAT12

Hi every one.
I have question about statistical analysis in CAT12. I use 2sample T-TEST for statistically analysis of two groups.In building statistical model I used global scaling with TIV. Setting is changed like below:
( Global Calculation → User → Global Values <-X → Define the TIV values here

  • Global Normalisation → Overall grand mean scaling → Yes → Grand mean scaled
    -value → Define here the mean TIV of your sample (or as approximation a value of
    1500 which might fit for the majority of data from adults)
  • Normalisation → Proportional)
    My question is that after changing this setting, which value should I specify for absolute threshold?(in default value:100)

This is a question for the SPM mailing list.
@CGaser