Please look at the next page(s). You may find the missing search results there.
The reason is that the advanced search in the Explorer sorts only search results displayed on each site. Only up to 100 search results can be displayed on one page.
E. g. When you have more than 100 results and you want to find out all diagrams where "consultant X" is set, you can sort the names of the attribute "consultant" for the search results. However, you will only see all search results for "consultant X" which are displayed on page one, even after sorting by name. The results of the next pages are handled independently. The next page may show you more search results. Again, sorting by name will sort all results from this page only.