Allied Telesis AT-S63 - Manual (Page 382)

Chapter 23: Protected Ports VLANs
382 Section V: Virtual LANs
Clicking repeatedly on a port toggles the port through the following
possible settings:
7. After making the necessary changes, click Apply.
Note
Untagged ports that are added to a VLAN are automatically
removed from their current untagged VLAN assignment. Untagged
ports that are removed from a VLAN are returned to the
Default_VLAN.
Removing an untagged port from the Default_VLAN without
assigning it to another VLAN will leave the port as an untagged
member of no VLAN.
Untagged port
Tagged port
Port is not a member of the VLAN