The Priority column on the Group Assignment Rules page shows the order in which EMS applies group assignment rules.
In the example below, consider an endpoint where FortiClient was deployed using the "HQ" installer ID and has an IP address that belongs to the 192.168.0.0/24 subnet. The endpoint applies for two rules. In this case, the endpoint is placed in the HQ group, since the HQ rule has a higher priority level than the 192.168.0.0/24 subnet rule. However, if the HQ rule is disabled, the endpoint is placed in the West Coast/Seattle group, as per the 192.168.0.0/24 subnet rule.