Reviewing journal files of your Revit sessions, you notice warnings related to "Invalid Spec" or "Unit Type <unit> does not specify default format options" and you want to know if these warnings are harmful to the file.
Issue: Journal file list debug warnings related to "Invalid Spec" or "Unit Type <unit> does not specify default format options".
Cause: The file you are working with was opened in Revit 2021.1 (or later point release) at some point. Now you are working with the file in Revit 2021.
Solution: Upgrade to 2021.1 or new version of Revit.