The extra assignees or inventors appearing that you did not search for are likely one of the following, depending on the type of assignee search you've done:
- Co-assignees - When for instance, Apple and Beats are both registered as an assignee on a patent, then when I search "Apple", Beats would show in the filters.
- Previous owners - When you've searched for current assignees, then the previous owners would show in the "original assignees" filter.
- Current owners - When you've searched for original assignees, the current owners would show in the "Current Assignee" filter.
The second two points are less likely, as we tend to search by, and show only current assignees unless you manually specify otherwise.