This reports what percentage of the card's dedicated frame-buffering memory, used to hold frames or cells in transit, is currently occupied. Sustained high values here, as opposed to a brief spike, indicate the card can't drain its frame buffers as fast as traffic is arriving, which is an early-warning sign for frame or cell discards before discard counters actually start climbing. For example, cardFrameMemoryUtil holding steady above 90 percent during peak hours predicts the onset of discards well before any drop counters register the problem.