Symptom
You give a discount of X% on item level in quote ABC (ABC represents the quote ID) but it's displayed on total level as Y, abc% (where X=discount and Y,abc=total given discount to be use in this example). These values don't match and is therefore confusing. You expect the total given discount to be X%.
Environment
SAP Cloud for Customer
Reproducing the Issue

Go to the Sales Work Center.
 Go to the Sales Quote view.
 Open any Quote.
 Go to the Pricing tab.
 Under item pricing, expand an item to see all its price components.
 Apply a product discount of X%.
 Observe.
The total Given Discount is now reduced to Y,abc%.
Cause
This is a rounding issue due to the numbers you have chosen. Prices below are examples to show the calculation:
For example, in quote ABC if the Price is 62,25 USD. The user applies 5% discount, 5% from 62,25 USD is 3,1125 USD. Hence, total value would be 59,1375 USD. However, as USD has only 2 decimals this has to be rounded to a discount of 3,11 USD and a resulting total value of 59,14 USD.
If you do this computation manually [3,11 * 100% / ( 3,11 + 59,14) ], then you'll receive 4,99598... that is displayed as 4, 996.
So the system calculates correctly.
Resolution
This is expected system behaviour.
The Total Given Discounts (%) in the Total Pricing section is calculated backwards from the values as it summarizes the discounts of all items and also discounts given on header level.
Keywords
% calculation sales quote, pricing , KBA , LODLECQP , Customer Quote Processing , How To