This value reports what percentage of the NPM (flow-processing module's) active flow-cache table is currently occupied, out of its fixed total capacity, exactly as the description states. Because the flow cache has a fixed number of slots for tracking active flows, a percentage climbing toward 100 signals the module is about to start evicting or failing to track new flows, which directly degrades flow-based accounting or policy decisions running on that module. For example, a reading of 92 means the cache is 92% full, and a burst of many short-lived flows arriving right after would likely push some existing flow entries out prematurely.