The critical SRF value is a global factor of safety similar to the Factor of Safety computed by a limit-equilibrium program. It is recommended to do a limit-equilibrium analysis as well.
The displacement data within a slope, for a particular SRF, are relative to SRF=1.0. To get absolute values of displacement, as are plotted in the shear strength reduction plot, go to the Data>Stage Settings menu option in the Interpreter. In the Stage Settings dialog, define the Reference stage as not used. Remember, displacements for SRF values represent the displacement if you reduce the shear strength in the slope by a particular SRF value. They are not the in situ values.
The examples shown below are taken from Tutorial 8.
Displacements for SRF=1.15 relative to SRF=1
Displacements for SRF=1.15 (Reference Stage not used)