If your are the owner of a business process, and you see yourself having to deal with customers' complaints more than 10% of your time, you have a problem. We chose the weight of 10% randomly. If you work 10 hours a day, then you would had no more than 9 hours left to devote to other things. This means that you are, at least, 10% worst off. The proper definition of output in the context above is: you have customers and more than 10% of them complain, and the proper definition of outcome in this context has the same meaning as output in this context. When you first open your doors, I would doubt that loosing more 10% of your customers was your focus. I trust that your expectations were different than that. You wanted to be the best businessman, who serves his or her customers to the best of abilities. You wanted to be on top of your game—your expected outcome, or your outcome goal. Your failure, however, is you are, at least, 10% down from the top of your game. That is the outcome; I would assume you did not anticipate.