Unknown symbol (Links panel)

[defaultmo2by4uy14u2]

Hi everyone! 

Last week a collaborator sent us an InDesign file, and when we opened it, in the links panel, appeared this unknown symbol  (image attached). Could someone tell us what it indicates? Thanks to all!

[Eugene Tyson · Accepted solution]

If you go to the sub menu for the links panel you will be able to see an option for what items are displayed.

This should tell you what the column is assigned to.