Tracking performance, availability, and quality scores each on their own process behaviour charts may help you to improve your processes. Each of these metrics may reveal signals of degradation or improvement, the investigation of which can impart the process knowledge necessary to operate processes more consistently. 

Multiplying these three figures together doesn't make any sense, though, and treating the product of the three as something important can only lead to numerical jabberwocky. In context, the data streams of the performance, availability, and quality scores will add up to a story about the things that you care about as a manufacturer; multiplying the figures together is a conscious choice to care less about this story and care more about abstracting meaningful data into a meaningless numerical value.