"Net 7" is an accounting term that describes when your invoice will be paid.  Your invoice will be paid 7 days after the last earnings date in your invoice.

In the 'Payments' module under the 'Date' column, you'll see that the date range for your earnings.  Your payment will be due 7 days after the last date of your earnings range.

For example, if your invoice 'Date' range (in second column) says 10/24/2016 - 10/30/2016, your invoice will be paid 7 days after 10/30/2016.