Data explorer returns only a certain number (500?) of items in the web interface. Too see them all you need to download them and look at them some other way (i.e., download a csv and open it in a spreadsheet).
It would be nice if it were easy to know how many items had been returned. What I’ve done in the past is to generate a second query that just did the count, which I find rather painful.
When the query is completed, would it be easy to pull out the number of results and print it next to (or below) the query completion time?