What is the function of Snap Vias

In the IC mode, how to use the snap vias option?

In the IC mode, there will be special layers known as Via layers. If you select any of these layers, or just a few vias, and click Snap Vias, HFSS will change the cross-section of the vias to match the cross-section of the top or bottom pads, provided that the delta is smaller than what was specified in the setting.