What does the 'DE-SCALE' message mean and how do I fix it?

The 'DE-SCALE' message indicates that calcium deposits or mineral scale has built up in your brewer and is interfering with performance. To de-scale, fill the water reservoir with undiluted white vinegar, run three large mug brew cycles without a K-Cup, then let the brewer stand for at least 4 hours. Next, fill the reservoir with fresh water and run brew cycles until the reservoir is empty, repeating as needed until any residual taste is gone. If 'DE-SCALE' is still displayed after completing this procedure, repeat the entire de-scaling process.