Question

How do we consider that a p orbital in benzene consists of 6 electrons?

Answer 1

It does not! No `p` orbital can hold more than two electrons, as per the Pauli Exclusion Principle.

---

Each `p` orbital on average contains only `1` electron. It delocalizes electron density throughout the ring so that each `pi` interaction shares one electron. That is, the electrons get smeared around the six orbitals evenly.

The SIX `p` orbitals will contain SIX total `pi` electrons, but each one holds on average one at a time.

Here is another depiction of that delocalization.