Understanding "Default mapping" function/purpose?

[henrypool]

Hello. I am trying to understand the function or purpose of the "default mapping" when editing dynamic zones.

I can not find any info about it online nor even in the Fortimanager's admin guide. 

I thought that if I added some interface names then all the matching interfaces would be assigned to this zone. For example see the screenshot:

This would be useful if I had several Fortigates in the same ADOM and this way I could have all Fortigates' wan interfaces assigned to the WAN_INTERFACES zone at once. Or do I have a completely wrong idea? 

It would be very helpful if someone explained the purpose of the "default mapping". Thank you!

[chall_FTNT]

If you only use "default mapping" for that zone as per your example, then when installing a policy package referencing that zone, the zone that will be pushed to each managed FortiGate will be wan1 & wan2.

Per-device mapping then overrides that default behavior for select FortiGates.  This is useful if you have 1 or more FortiGates which include different interfaces in that zone ... ex, port1 & port2.