What are two characteristics of FortiGate HA cluster virtual IP addresses?

Fortigate Infrastructure 7.2 Study Guide page 301

FortiGate Infrastructure 7.2 Study Guide (p.301):

"FGCP automatically assigns the heartbeat IP addresses based on the serial number of each device. The IP address 169.254.0.1 is assigned to the device with the highest serial number."

"A change in the heartbeat IP addresses may happen when a FortiGate device joins or leaves the cluster."

"The HA cluster uses the heartbeat IP addresses to distinguish the cluster members and synchronize data."

https://networkinterview.com/fortigate-ha-high-availability/