This counts NR-RB RAPS PDUs transmitted out this node's west link, which only has meaning if this node is itself the RPL owner for this virtual ring per the west-link RPL object. A nonzero, incrementing value here confirms this specific node is actively performing its RPL-owner duty of periodically announcing the healthy-and-blocked state to the ring; if this stays at zero despite the RPL object showing owner, that's an inconsistency worth investigating. For example, an admin auditing which physical node truly holds the RPL-owner role for a given virtual ring could confirm it by finding the node where both the RPL object reads owner and this transmit counter is actively climbing.