RC quality graph in Flight Review - what does it mean?

I’m trying to understand how to interpret the RC Quality graph in Flight Review. It has values from 0 to 1. What does this number represent? And why does it sometimes change during a flight? Does it relate to range, and does a low number mean there is a reduced range? I get common numbers like 1.0 and 0.24 on many flights. One flight started at 0 and steadily climbed to 1.0 during the flight. I’d appreciate some input on this.