This read-only counter holds the high-word of the count of packets permitted by this rate limit, with the description explaining that ccarStatSwitchedPkts holds the lower 32 bits and this object holds the high word once the count is too large to fit in 32 bits, meant to be combined by an SNMP manager into a full 64-bit total. This object only becomes meaningful once ccarStatSwitchedPkts itself has wrapped past its 32-bit ceiling of roughly 4.3 billion packets, so on a link busy enough to hit that volume, a manager needs to combine this high-word value with the 32-bit counter rather than relying on it alone, which would otherwise appear to reset to a small number after wrapping. A high-traffic interface where ccarStatSwitchedPkts has already wrapped around once would need this overflow counter's value combined with the current 32-bit count to get the real total packet count since the entry was created.