Yes, our GoToWebinar Integration enables you to track attendance, no matter how many webinars a Lead or Contact has Registered for and or Attended. See the image below as an example of a Lead who has Registered for multiple Webinars. 

Users gain full insight into any Lead or Contacts Webinar History, including the Webinar Title, Date, Date Organizer Name and Attendance.

Related List view of Webinar History from Lead and Contact Objects

Within each individual Webinar, users can also see the attendance details from the "Registrants" sub tab. Notice the "Attended" column flags who has Attended your completed webinars. In the example below only 2 of the 6 Registrants actually logged in to this Webinar. 

NOTE: By clicking on the "Link" url, users is taken directly to that Contact or Lead record, where that records entire Webinar History (as shown in the image above) is then available.