Hi @mwilhelm,
In that case I’d recommend approaching this from a different angle, assuming that you are on a Professional or Enterprise subscription – since you can create custom reports?
Start by creating a custom date property, e.g. Subscription date. This date would be set by a contact-based workflow: Enroll contact when they are subscribing, set property value of Subscription date to date of step.
You can then create a custom report: Menu > Reports > Reports > Custom report builder with primary source contacts. Drag and drop the new Subscription date into the X-axis, the Count of contacts into the Y-axis and the Unsubscribe date into Y-axis 2 where it will be transformed into Distinct count ( Unsubscribe date ).
Unfortunately, with two data points on the Y-axis, you can’t set the chart visualization settings to cumulative. That would only be possible with one line of data. However, you’d see how many contacts were “added to your list” (= have a Subscription date) and how many contacts left the list (= have an Unsubscribe date), per month (or other time interval). I’m not aware of any better way to visualize this (e.g. cumulative visualization that automatically drops when someone unsubscribes).
Hope this helps!