I thought all Google Sheets don't take up storage quota. What does this mean?
There are no picture clips or anything additional to the last file than the others.
Google changed the Google Drive storage policy. Old files that have not edited recently will not count against the quota but new files and edited recently files will do. For details see Changes to Google Workspace storage policies starting June 1, 2021
In the specific case shown in the screenshot, the files no counting against the storage quota have not been modified this year the one that is, it was edited this month.