The default values for the Digit Symbol (or digit separator), Decimal Separator and the number of Decimals of measurement units are taken from Windows' registry. The values are defined in Windows' Regional Settings dialog's Number and Currency page.
If you choose to personalize these values, instead of using the Windows default values, you gain the possibility to have a common appearance for values (i.e. the values would not change from user to user due to personalized regional settings).
With the options to modify the display of your measurement units, you have more possibilities to customize QPR Metrics for your organization's needs.
More about Measurement Units.