Choose source and destination ports (or ranges of ports) here.

Ports choosing available only if any PORTS-based protocol is selected on Protocols tab.

If "Enable reverse checking" option checked, rule can do following:

if rule source port(s) and packet source port comparison does not evaluates to True and rule destination port(s) and packet destination port comparison does not evaluates to True - rule makes the reversed check with opposite source and destination ports. It allows to use one rule for both directions of packets.