Exactly as described, this is a running total of 802.3x flow-control PAUSE frames this benchmark port has transmitted. A benchmark test port transmitting PAUSE frames means the port's own receive buffers are filling up faster than it can process incoming traffic, which would throttle the far end and directly distort a throughput or frameloss test result by making it look like a link-capacity problem when it's actually local buffer congestion. For example, PAUSE frames climbing during a high-bandwidth throughput test would explain measured throughput coming in lower than the theoretical link rate even though no frames were technically lost.