The total result count returned with the results of some search queries is not exact.
The total result counts for any given query are an estimate determined by Search Server based on a subset of the total results in the index. The number of results in the subset used to generate the estimate canbe thought of as roughly (# of Previous Results) + (4 * Page Size). This ensures that the early pages in your result set, which see a majority of the traffic, perform efficiently. As a user pages more deeply into the result set, the total row count narrowsin on the exact count as a larger subset of results is being processed to determine the estimate.