Here I have 25 squares and 1 surface which I have Copied>InPlace to create dupes.
I enable the selection filter with just surfaces checked to select just the duplicate surface, and I get this report on the command line:
Command: SelDup Found 26 duplicates. 1 surface added to selection. Duplicate selection is from model space only.
It does correctly report that only one surface was added to the selection, but the “Found 26 duplicates” should not be reported IMO…