What’s The difference between CRI and Ra

What makes the difference in Value between CRI and Ra:
 

Usually, we always tell the quality of color by value of CRI, but it always show like this CRI(Ra). As we know the value is different  though the same definition of color rendering index.
 

What makes the value difference between of CRI and Ra?
 

Let us see the calculation. Ra is the average of R1~R8, while CRI is the value of R1~R14, so the values are different. But why the CRI value always lower than the value of Ra? If that means the value of R9~R14 is not as high as R1~R8, the answer is definitely, especially R9(strong red). For example some lights with Ra85(maybe CRI 82), but R9 is around 0, even below 0. that's quite terrible and R9 is very important for truely color, it is the basic color of the daylight.
 

Now more and more people are pay attention to the value of R9, and some new standards are proposed such as CQS.