This read-write integer is a bitmask selecting which error types (CRC errors, runts, out-of-window collisions, alignment errors, an undefined bit, and giants) are summed for the error alarm on this specific port group (board). Admins customize it per board to focus the alarm on the failure modes relevant to that board's hardware or media type. Leaving out a relevant error type here means the board-level alarm could miss exactly the failure an admin most needs to catch.