This is less straightforward than I'd expected,
- Instances only have there elements counted once for the unselected number.
- The selected number counts every instances.
This means if you select 3x linked cubes it shows
The vertex count as 24/8 which seems odd.
We could put this patch on hold since it's not high priority.
What if we just show the vert\poly counts for real geometry as the first step of implementation of this feature?
This is very useful in modeling\game development. Lets treat the issue with instances as some sort of limitation, rather than a bug =))