how to find change in position of a point with change in load on a cantilever structure

Hello,

I'm a learner of comsol. i want to find change in lattice constant of a Photonic crystal structure which is made on the free end of a cantilever structure. I did simulation and i got point graph load Vs Total displacement. This plot consists of two straight lines. I want to know what these two lines convey. In the settings of point plot i have added two successive holes on the photonic crystal structure to see the variation of lattice constant of PC srucuture. Please see the attached plot and please help me in this regard.

regards