This option is used to create a new Check for a Table. For tables that do not already have an Order assigned, you can click on the Table on which you want to start a new Order and bypass clicking on New Order.
Select the New Check option at the bottom-left.
Select a Table.
A number pad pop-up appears. Enter the number of Seats for this Check.

Press Continue. You will be taken to the Order screen where you can start the sale, and view the number of Seats.
The Seat Count pop-up can be disabled in POS Settings on the terminal. This is a terminal specific setting.