The dialog "Add Ports" in Firewall Other ports has the label "Port(s)", implying that it's possible to enter multiple ports in the same entry. However, it complaints on port ranges like 6881:6999 (which is accepted by iptables) and doesn't accept comma-separated ports too. (message: Invalid port given) Please allow this. Thanks!
Use a dash for ranges. Instead of trying to separate several ports with commas, use the add button to add another entry to the table for another port.