This article explains the behavior when FortiGate is in an HA cluster and Standalone, the file name will be different.
Scope
FortiGate v7.0 and above.
Solution
Automation backup file name will be generated by the string customized in ‘Automation Action’, for example, the automation script executes backup config tftp My_config_Name%%date%%.conf 192.168.1.1. The name of the file name will be ‘My_config_name2024-04-26’, see screenshot below, you can change My_config_Name to a custom string.
Refer to this KB article to configure Automation backup with date: Automation backup with date
After v7.1, change will occur when FortiGate is set in the HA Active-Passive cluster. Refer to this related document: Resolved issues
Above FortiOS v7.1, the automation backup file will append the device serial number in the file name. This is expected behavior, see a screenshot of the backup result when the device is in the cluster