This object selects which statistic, bytes, packets, or bit rate, the rising and falling threshold values configured elsewhere in this row are actually measured against. It matters because a threshold value like 1000000 means something very different depending on whether it is being compared against a byte count, a packet count, or a bit rate, so getting this selection wrong would make the configured thresholds essentially meaningless. Choosing bitRateSum here means the paired rising and falling thresholds are interpreted as combined in-plus-out bits-per-second limits, not raw traffic volume totals.