This read-only value reports the default (baseline) amount of packet buffer the ASIC reserves or grants to this port before any dynamic sharing kicks in, for this specific physical interface (ifIndex-indexed table). An admin compares CurrentUsagePerPort against MaxLimitPerPort on a specific port to see how close it is to its buffer ceiling, which is the classic early-warning sign of an oversubscribed or bursty port about to start dropping traffic.