Analysis tools
Check your chapter's number by Jackie Han
A page to help you understand the size of your events in the past:
https://script.google.com/macros/s/AKfycbxhUrO0-2JUBpw60pc8JYt77PMESyex4b6-JNvopbTboV2JIaSL/exec
See also the analyzing section.
Statistics about using your event's short url
For each GDG event, the firefly project (http://gdg.events) creates a short url that tracks which users have used the link. You find the statistics at the firefly url appending analytics, e.g. gdg.events/78dd40/analytics for GDG DevFest Berlin.