In compact cell view the index number is not shown. I also far preferred the large size index number, is there any way to have the bigger size back ?
Hit 'J' to toggle through the views and hit 'Ctrl+J' to set the detailed options for every view.
I have seen reports from others that the large index numbers are not appearing - a 'bug' in the latest LR version. It may be specific to Mac users running the Sierra OS.
As above- Small index numbers can be shown on the thumbnail borders with the Ctrl+J options.