When I search something in the Explorer, there is mentioned "(found in roughly XX objects)" but the number changes every time I click on "next page".
For performance reasons, the amount is an estimation. The number can increase and decrease while browsing through the result pages.
However, the count of search results on the last result page is always the correct number and will be more and more accurate the closer you are to the last page.
KBA , BPI-SIG-CA-SEA , Search for SAP Signavio , How To