IPS Instances Question

All-

I am in question about the number of IPS instances and have some questions.

1. What is the number of instances recommended per CPU? Example on a core 2 duo if the recomended instances is 1 per CPU would one then set 2 instances (cc set ips num_instances 2)?

2. Secondly on a fresh reload of UTM 9 with HTTP, IPS running when using CLI and running cc get ips num_instances, it is set for 0 although when reviewing Webadmin>support>advanced>Process list there is one process of IPS (snort).

In my understanding instance would equal process. 1 instance, 1 process in the process list. If the fresh reload has a setting of 0 instances why is a process displayed ? Does 0 allow the software to add snort process as needed?

Thanks,
Jim