This is the 64-bit version of cefStatsPrefixInserts, counting FIB insert operations for a given prefix length without wrapping as quickly. On a core router that processes a full Internet routing table, insert counts for common prefix lengths like /24 can be large enough that the 32-bit counter wraps between polls, so this is the object long-term trending tools should graph. A capacity-planning dashboard tracking FIB churn over a month would rely on this 64-bit counter to avoid a false negative-growth reading caused by a 32-bit counter wrap.