This read-only counter holds the high-word of the count of bytes which exceeded this rate limit, meant to be combined with ccarStatFilteredBytes once that 32-bit counter wraps. Combined with ccarStatFilteredBytes, it gives the true cumulative volume of traffic that exceeded this entry's rate limit over the object's entire lifetime, useful when justifying a rate-limit policy change with total excess-traffic volume rather than just a recent sample. Reporting that a rate-limit entry filtered 50 GB of excess traffic over its lifetime, to justify raising the configured rate, would require combining this overflow object with ccarStatFilteredBytes.