[Freesurfer] Question of longitudinal processing

Hello list,

I have a simple question about the LongitudinalTwoStageModel tutorials on freesurfer website.

It is from this link https://surfer.nmr.mgh.harvard.edu/fswiki/LongitudinalTwoStageModel

long_mris_slopes --qdec long.testretest.qdec \ --meas thickness \ --hemi lh \ --sd $SUBJECTS_DIR \ --do-pc1 --do-label \ --generic-time \ --fwhm 15 \ --qcache fsaverage \ --stack-pc1 lh.testretest.thickness-pc1.stack.mgh \ --isec-labels lh.testretest.fsaverage.cortex.label

My question is, what is the content of long.testretest.qdec ? I understood till 1st stage was done, we got only one file which is long.qdec.table.dat.

Could anyone help to clarify my question?

Thanks a lot Jahanvi