EX2 Ultra Backup Operation and Settings

I have a 4TB EX2 Ultra NAS. My intention is to connect 2 external USB HDD’s to it for Backup. My plan is to rotate the external HDD’s on a weekly basis for Disaster Recovery Off-site storage. I do NOT see any explanation about how the backup feature functions. There are several Backup Types but no documentation on their differences.

Specifically, I see nothing about the “Auto Start When Connected feature.” Is there any documentation on this? The name of this feature implies that when it is off, the unit operates differently and I’d like to understand what these two modes are about.

Also, during a backup, there are number displayed e.g. 6/9 and I would like to know what these numbers mean. I again, do not see this in the documentation.

Finally, how do the backups work? They appear to be continuous but what causes a backup to start? I am currently configured for a full copy and NOT to Autostart Upon Connection. Should I be concerned with connecting and removing external HDD’s? The lack of documentation is very disturbing to me.