A service provider is migrating from LDP to Segment Routing on an IS-IS enabled IOS XR core. An engineer configures a Prefix-SID index of 100 on the loopback of router PE1. The default SRGB across all routers is 16000-23999. When PE2 forwards traffic toward PE1's loopback, which MPLS label value will PE2 impose for the Prefix-SID?