In the section "Rescue" you can reopen (rescue) tables that have already been settled. The respective invoices are logged here. On your iPad, tap "Admin" and select "Bill Management" in the following screen.
Here you can see all the tables that have been settled. If you want to save a table, touch the desired invoice.
Now click on "Save" to reopen the table.
Confirm your selection by pressing "YES".
In general the steps are as follows: