The 95% confidence number means that it is likely that you have *some* common ancestor in the range listed. When you look at the details, Ancestry is highlighting surnames that are found in both pedigrees as a visual aid, not claiming that the person listed is *the* common ancestor responsible for the match.
I don't have an example in my own results, but I've seen a screen print of a case where Ancestry did identify a specific person as a candidate for the common ancestor. It showed lines of descent for the two sides. I can't dredge up the URL right now, but maybe someone else has an example.