Explaining the Siemens Disconnect and Parallel Wiring

What happens here

The electrician points to the Siemens disconnect within the panel and explains that it's a 400 amp, 480 volt system. He shows the 3/0 conductors used for the main phases and a #2 ground wire. He then elaborates on 'parallels,' explaining that instead of one large conduit feed, two smaller conduit feeds are used for practical reasons, and emphasizes the importance of ensuring the equipment grounding conductor meets the overcurrent protection device's requirements.

Goal: Detail the specifications of the disconnect and the concept of parallel conductors.