If the url shortener using same script like others i have an idea with that.

On the settings they can choose if the views will be global or per campaign.


Global - all shortened links are unite as 1 means if i click on shortened link my ip will be counted as view globally for 24 hours even if i click on different account it will be marked ad counted since the views are global.

For example

Campaign1 - all clicks will be marked as unique
Campaign2 - will not count since ip is registered globally


Per campagin - if they choosed per campaign means for every campaign all are unique views

For example

Campaign1 - 1 unique ip
Campaign2 - the same ip but also counted as unique on this campaign.