Do you use placeholders from time to time during projects?
If you upload an equipment list with a placeholder value in the TAG field (i.e. NA or N/A etc), normally you will NOT want to show the placeholder tag on tag lists for documents. This can happen when the level groups more than one tag together.
To hide the placeholder values, just add them to the Ignored Values list under the settings menu. You can include as many values as you wish. But remember this is for all projects, so only list true placeholder type values here.