When configuring SLA for an extension, how can the primary extension dial out as another extension or business, and what is the significance of assigning a unique caller ID to that profile?

Significance of assigning a unique caller ID to the profile

Configuring Shared Line Appearance (SLA) allows the primary extension to dial out as another extension or business by choosing the SLA button. Assigning a unique caller ID to that profile is significant for distinctive identification, useful in environments like law offices or medical practices with distinct departments