Reference
Datacenter IP pool size
The shared datacenter proxy network is comprised of thousands of IPs across multiple subnets with a new IP assigned on each request you make.
The Shared datacenter IP pool is comprised of 10,000+ datacenter IP addresses across multiple subnets.
IP’s in the pool are frequently rotated and changed.
Setting up a zone on the Shared datacenter network
You’ll receive a different IP on every request you make to a zone on the Shared datacenter network. If you want to reserve a specific IP pool for your exclusive use you should set your zone up against the Reserved datacenter network.