Instantsearch does two searches: 1) To fetch results with the filter applied 2) To fetch facet counts without the filter applied It then shows the facet counts from 2) in the UI, which is what is causing the confusion. Because once the filter is applied and we do a vector search, there are now more results with that author that are fetched. This is a quirk of how vector search works (because we only look at top K matches).