These two phrases describe the same group of people two different ways. AT: "the leaders of Israel who are also the heads of their ancestors families" (See: [[rc://en/ta/man/translate/figs-parallelism]])
Here the leaders of the families are referred to as "heads." AT: "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. AT: "had helped Aaron and Moses to count the men" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
# They brought their offerings before Yahweh ... They presented these things in front of the tabernacle
This means that they gave their offerings to Yahweh and brought them to the tabernacle. These phrases may be combined to add clarity. AT: "They brought their offerings to Yahweh and presented them to him in front of the tabernacle" (See: [[rc://en/ta/man/translate/figs-explicit]])