1. Open the image/record in Transcription screen, and the image number will be on the left of the line showing the Cemetery name (and if untranscribed - name of photographer).
2. For numbers of adjacent images, at the bottom below the photo, click on the LINK button and it will open a new window showing linkable photos.
3. The actual image numbers are in blue on each photo. If they are too small for you to read, try to enlarge using Ctrl+ keyboard shortcut.
I think this is the only way to see these numbers, but maybe someone else knows another way.