How to calculate target number of documents in my organization rating chart

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Can someone explain how to calculate the target number of documents in the my organization rating distribution chart ( My team> Performance> My organization> rating distribution)  available for a line manager ?

There are 5 performance rating levels.

Example : Performance Rating Level : Needs Improvement

Manage Target Rating Distribution > Needs Improvement > Distribution Percentage > 20

Manage Model Profiles > Performance Management Model> Needs Improvement > Distribution Percentage > 0-20

 

For a particular performance document it showing 5.4 as the target performance documents and the actual number is one. 

I can not understand the logic behind this calculation. And again it always showing decimal numbers.