This counter tallies packets shorter than 64 bytes received across all ports in a group that otherwise contained no errors, i.e. legitimate runts rather than corrupted fragments. Because standards-compliant Ethernet frames are never under 64 bytes, a nonzero value usually reflects test traffic or a non-conforming device attached somewhere in that group. An admin noticing this counter rising on group 2 would look for a misbehaving NIC or diagnostic tool plugged into one of that group's ports.