This document explains how an IP address is assigned to a GlobalProtect client when two or more IP address pools are configured.
Palo Alto Networks firewall keeps a pointer to the pool from which the last successful IP address assignment was taken. The next client will get the next available IP from the pointer's pool.
192.168.10.0/24 > pool-1
172.16.10.0/24 > pool-2
*pointer > pool-1
How can IP Overlaps be Prevented with GlobalProtect