Marketo allows you to set the maximum number of people that can qualify for a smart campaign; this helps you avoid accidentally emailing your whole database. If you want to override this limit, here's how.
Be sure to enable person restrictions for smart campaigns in Marketo Admin.
1. Find your smart campaign and click Schedule.
2. Click Qualification Rules.
The default limit is the one set in Admin.
3. Next to Abort campaign if qualified leads exceed, enter a new limit.
The smart campaign will not run if the number of people who qualify exceed the set limit.
Be careful with this feature so that you don't accidentally include too many people.