When you get to your homepage, the first thing you will see is your Subscriber Dashboard Graph.
The graph measures how your Forms are performing and measures the number of opt-ins, not necessarily unique Subscribers.
The "TODAY" number represents how many opt-ins you have received today.
The "7 DAY" number represents how many opt-ins you have received in the last 7 days.
The "30 DAY" number represents how many opt-ins you have received in the last 30 days.
The "TOTAL" number represents the total number of unique, active Subscribers in your account.
The bar graph visually represents opt in to particular Forms. If you hover over particular bars, you will see total opt-ins to that Form, on a particular day:
The default view of your Dashboard is the last 30 days, but you can change this range:
Select the date range you'd like to view, and your graph will change, and show you your total for that date range in contrast to your current account total: