Allied Telesis AT-S39 - Manual (Page 160)

Section II: Local and Telnet Management
160
Undersize Packets
Number of packets that were less than the minimum length
specified by IEEE 802.3 (64 bytes including the CRC) received on
the port.
Fragmented Packets
Number of undersized packets, packets with alignment errors,
and packets with FCS errors (CRC errors) received on the port.
Oversize Packets
Number of packets exceeding the maximum specified by IEEE
802.3 (1518 bytes including the CRC) received on the port.
Port in Discards
Number of frames successfully received and buffered by the port,
but discarded and not forwarded.
If you want to clear the counters on the port and return them to “0”,
select the option “2 - Clear Port Statistics” from the Port Statistics Menu.