Where can I find out how my contacts were added to a specific list?
From the Dashboard, go to Reports and click on Contacts to get to Subscription statistics. Select the list you’d like to review the numbers for.
After choosing lists to view, you can define a date range. View subscriptions by source in the How new contacts were added section.
View unsubscribe reasons in How contacts were deleted.
If you prefer, switch to list view by clicking on list name in List trends. Daily data is displayed in individual rows with the totals and averages below the table.