The default ADC report template contains a DAR calculation which is suitable for intact ADCs.
It's relatively straight forward to adapt this report template to calculate DAR for reduced molecules.
To do this, open the default report. If the default ADC report is not already loaded it can be done so by selecting File>Presets>Report presets>Intact_ADC_Report_withPlots.rptc
Once the report is open, the option to calculate DAR for a reduced antibody can be added by clicking on File>Presets>Tab presets>Intact_DAR_Fraction_Reduced.tabc
Once selected a new tab DAR Fraction Reduced will appear: