Please check with the person who had given you this excel sheet. This is a classic example of misunderstaning the concepts and using them erroneously. What you call bell curve is actually "Normal Probability Curve" (since it is bell shape it is called bell curve).
Normal Probability Curve (NPC) is an ideal distribution plot of any measurable chararacteristic that is supposed to be normally distributed in the larger population. For example; if you measure height of all people in the world, the distribution of the height will be close to the NPC (but it will never be exactly like that).
This is misuse of NPC to project it as ideal in small samples that are conceptaully "not normally distributed" e.g. if you plot the IQ of IITians it would never be similar to NPC as IITians are supposed to (are actully are) be on the higher side.
This is a misconception that general big NPC is composed of sevel small NPCs. The graph here is a complele misrepresentation of the applicability of the concept.
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Can you please help me in describing the fields, as I am doing the appraisal first time
My rating scale is
Whether I had to put the above rating in Rating or in Recommended
How you had put the % in Ideal bell curve