This read-create field is only meaningful when the ACE's action is deny or deny-DisablePort, specifying the particular drop behavior to apply. It matters because deny traffic can be handled in more than one way, for instance simply dropping packets versus also disabling the port, and this field selects which. For example, an admin wanting a security violation to shut down the offending port entirely, not just drop its packets, would pair a deny-DisablePort action with the appropriate drop type here.