RobH_en_tn/num/07/02.md

the leaders of Israel ... the heads of their ancestor's families

These two phrases describe the same group of people two different ways. Alternate translation: "the leaders of Israel who are also the heads of their ancestors families" (See: rc://en/ta/man/translate/figs-parallelism)

the heads of their ancestor's families

Here the leaders of the families are referred to as "heads." Alternate translation: "the leaders of their ancestor's families" (See: rc://en/ta/man/translate/figs-metonymy)

had overseen the counting of the men

The abstract noun "counting" can be stated as a verb. Alternate translation: "had helped Aaron and Moses to count the men" (See: rc://en/ta/man/translate/figs-abstractnouns)