From the Deployment and System Settings lesson, the Study Guide states:

" Other ports, with the exception of port3, can also be configured as management ports from CLI. "

" You can set additional ports as management port using the CLI command shown on this slide. "

From the Lab Guide (Exercise 4 - Using Inline Scanning) :

" FortiGate and FortiSandbox communicate through port 4443. Management or API ports grant access through port 4443. "

" Enter the following command to enable API access on port2: set api-port port2 "

Ports that are designated as either administration interfaces or API interfaces cannot be selected for 802.3ad aggregate bonding because:

Option A — Port 4 configured as an administration interface is reserved for management traffic and cannot be repurposed for link aggregation

Option C — Port 4 configured as an API interface is dedicated for API communication (port 4443) and is similarly restricted from being used in aggregate bonding configurations

Port 4 in the Lab Guide is specifically referenced as the HA communication and management port, confirming these restrictions apply when special roles are assigned to interfaces.