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The Quick View Number of Ancestors is similar to the text report Number of Ancestors. For each generation of the person's ancestors it tells you the number of ancestors found, the theoretical ancestor number and how many percent of the theoretical ancestors were found. The Quick View only counts individual ancestors, therefore duplicates caused by pedigree collapse are ignored in the calculations.
You can activate the Quick View by right-clicking on a person's name in the People Category View. Then select Quick View > Number Of Ancestors.
- Pedigree collapse - Wikipedia