0 replicants, 1 duplicates

If I do Show Info of a file (an rtfd file) that has several duplicates, there is a menu button at the bottom of the info panel at “Instances:” saying “0 replicants, 1 duplicates”.

However, there are several duplicates of the document, but no matter how many duplicates, the title of the menu button is always the same, saying that there is only 1 duplicate!? Pretty confusing to me! Is there something I have misunderstood, or is it plainly a bug?

PS: to be on the safe side, I also submitted this as a bug report.