Well ok.
Let's say I have rating of 3.5 and somehow I'll increase it to 8.3. What will be different or how this can help me?
The rating starts from 1.0 to 7.9.If u want to know more about your PC score go
My computer-->Properties-->Windows Experience Index(blu color)
There u will see your PC rating and u can learn more for it at 2 links below.