The number of required flex credits for a VM-Series firewall primarily depends on the vCPU allocation. Flex credits are used to license VM-Series firewalls, and the number of credits required is determined by the number of virtual CPUs (vCPUs) allocated to the firewall. Higher vCPU allocations provide greater performance capabilities and thus require more flex credits.
References:
* Palo Alto Networks Licensing Guide: VM-Series Licensing
* Palo Alto Networks VM-Series Datasheet: VM-Series Datasheet