This caps how many APS protocol messages can be sent within each cApsConfigMessageHolddown window when using the dcc, ip, or osc transport, working together with that holddown timer to define the overall rate limit for APS signaling traffic. This matters because it bounds how many protection-switching messages get sent even during a genuinely rapid sequence of real events, preventing the message channel itself from becoming a bottleneck or flooding the far end. For example, setting this to 3 alongside a 500ms holddown interval means no more than 3 APS messages can be sent within any given half-second window, regardless of how many triggering events occur.