Ad Hoc - Visitor Participation

I am looking at two different reports:

1. Tracking Code and Sign Up Page (Visitor Participation) metric. Tracking code = 1234

2. Sign Up Page Success Event report in SiteCatalyst with a visitor segment = tracking code 1234.

The Sign Up Page event is a plain counter and fires on every page load. 

In AdHoc I see a total count of 6, but when I run this report in Sitecatalyst the count is 11. Why is there a difference? Time period is exactly the same. 

Thanks