Less than 30 point features fall within the bounding polygon areas you provided. Only the points within the bounding areas will be analyzed. As with many statistics, a minimum of 30 features is required to produce reliable results.
Unfortunately, if you do not have at least 30 points, this method is not appropriate for your data. With a minimum of 30 points, however, the solution here will often be to provide different, perhaps larger, bounding polygon areas.
Another option would be to provide a layer with a minimum of 30 aggregation polygons that overlay at least 30 of your points. When you provide aggregation polygons, analysis is performed on the point counts within each area.