The Real thickness, cavity result is created only if you have modeled a core, and selected the Perform core shift analysis option in the Fill analysis advanced options.
It shows the part (cavity) thickness during the filling and packing phases of the molding cycle, taking into account the displacement of the core. The default display shows the thickness values in the part, at the time indicated on the top right corner of the display.
As the core deflects, the area of the part towards which the core deflects will be thinner, and the area of the part away from the deflected core will be thicker. The variations in cavity thickness can be seen by animating the result using the Animation toolbar.
By default, this result shows the thicknesses throughout the part by means of the Animation plot type.
You can also investigate the change in thickness over time at various locations on the part by creating a new XY plot or path plot of this result.