Follow-ups are prioritized over starting the campaign for new leads.
In other words, the system will first try and send all the scheduled follow-ups based on your campaign's settings. Once it has done that, it will start the campaign for new leads - assuming there is still time left in the schedule and the daily sending limits (for the campaign and for the associated accounts) have not been met.
This helps ensure that the system follows your schedule and campaign settings as closely as possible.
If you'd like to contact more new leads faster, you can change it by going:
To campaign options
Scroll down to the very bottom and click on "Show advanced options"
Click Save to confirm the changes
