Trafficback URL function is a great decision if you don’t want to lose your traffic which is non-valid by OS/GEO/DEVICE targeting at your offer. All the clicks which doesn't suit your offer settings restrictions will be sent to traffic back and won't be counted.
Also you can send all the traffic which is over the cap to trafficback URL by switching on this option
And after that all non-valid traffic will be sent to chosen URL
You can set global trafficback in the way you want. You can choose wether to use it if offer has suspended or stopped status/it's disabled for affiliate or just to use it when offer is not disabled (by any reason) but there are inappropriate user targeting, overcaps, etc.
If you still have any questions, you can ask them in comments or contact our support team