This read-only Counter32, valid only while a VRRP router is defined on this interface, totals received packets with invalid IP address list errors, meaning the set of addresses advertised didn't match what this router expects for the virtual router. An admin cares because this usually flags a configuration mismatch between VRRP peers over which IP addresses the group is protecting. For example, an admin who recently added an associated IP address to only one peer's configuration would see this counter increase due to the mismatch until both peers agree.