When the Index Numbers are displayed in the Compact Cell view mode in the Library Module, they appear very large, slightly behind the thumbnail (preview). The large number is legible until you find yourself working on beyond 100 images in a Collection especially when those images are vertical orientation. The Index Number becomes almost completely obscured by the thumbnail (preview), making it illegible and useless.
The Extended Cell view does alleviate this quirk by displaying the Index Number small, and above the preview. It just gets me right in the OCD that the Compact Cell view has this - albeit minor - annoyance.