Short.io displays every URL requested on your domain, even if it doesn't exist. Browsers send requests when you visit a page; the first is done to fetch an icon of a webpage (favicon); the second is done to load a requested web page.
The first request results in the URL with /favicon.ico, which you see in statistics.
How to remove
If you don't want "../favicon.ico" to be displayed in your clicks stream, you can filter it out. Navigate to Clicks Stream > Filters > Choose "Is not" for the path filter > Input /favicon.ico > Select the result from the drop-down list > Apply.