This is the Potential Surface Distribution from 2V to -2V.
Reference:
[1] Let’s Code Physics. “Potential from Boundary Conditions (Computational Electromagnetism 1).” YouTube, 17 Aug. 2020, www.youtube.com/watch?v=ksOkjshHU5Q&list=PLdCdV2GBGyXOV45Sojhe-zCEV9Oz-pxvJ&index=1. Accessed 3 Feb. 2021.