On SO when a search returns > 5,000 results it indicates the results have been capped a 5,000 by displaying the number of results as "5,000+"
On P.SE it only displays the "5,000" without the plus at the end. This lead be to believe there was only 5,000 non-closed questions on P.SE when searching on 'closed:0'.
Cosmetic issue, put I thought I'd raise it since it can cause confusion.