I see – well generally speaking using query_posts() like this a “bad idea”. From the WordPress Codex:
This function isn’t meant to be used by plugins or themes. As explained later, there are better, more performant options to alter the main query. <i><b>Double Note:</b></i> query_posts() is overly simplistic and problematic way to modify main query of a page by replacing it with new instance of the query. It is inefficient (re-runs SQL queries) and will outright fail in some circumstances (especially often when dealing with posts pagination). Any modern WP code should use more reliable methods
If you visit Events → Settings → General you should find an option labelled Number of events to show per page – does adjusting this get you closer to your goal?