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What do you mean discount? Are you looking for a discount percent of a calculated cell? If so click on the cell and look at the formula bar to see how it was calculated. If the is coming in from an imported table it gets a bit harder. It may have already been calculated before the import or is being done through a script.
If the discount is calculated in the sheet, click on it and look at the calculation in the formula bar. Is this data being imported? If so it may have been pre calculated or is being done via a programming script.