How to prepare Sentinel-1 images stack for PSI/SBAS in SNAP

Microwave Toolbox StaMPS
497

hi all
so what is the different between v-ds and v-d because when I plot using ps_plot. I got result as follows:
ps_plot(‘v-ds’)

v-ds.jpg1920×976 164 KB

ps_plot(‘v-d’)
v-d.jpg1920×976 156 KB

I’ve read the manual and there’s no description about v-d and v-ds variable