When you create a new Soapbox Mailer campaign, you might notice that there are numbers in your Email Campaign Performance section that show negative (and also positive) numbers. You haven't even sent off an email yet, so how can there be any metrics at all?
In Soapbox Mailer's Email Campaign Performance section, the top row of numbers in black are the metrics for your current campaign. Those will likely all be set to zero. The second row of numbers directly under the top row of numbers measure the relative difference between your current campaign and all your other Soapbox Mailer campaigns. Since there exists a value for the average of your other campaigns, it comparers this to your current campaign's zero values, and provides the difference.
In short, regardless of your Soapbox Mailer campaign's status, the comparative values will always appear and compare your current campaign to your average across all Soapbox Mailer campaigns. This can result in both negative and positive values even before you send your first email.