This counts VRRP advertisements this router received where the sender's priority was explicitly 0, the special value a master sends specifically to signal it's voluntarily relinquishing the master role so a backup should take over immediately. A backup router seeing this counter increment should correspondingly show a near-simultaneous transition to master in cVrrpStatisticsBecomeMaster, confirming the handoff was a clean, intentional one rather than the master silently disappearing. If this counter shows an increment but no master transition followed on this router, that inconsistency itself is worth investigating as a potential VRRP state machine problem.