עִזִּ֣ים מָאתַ֔יִם וּתְיָשִׁ֖ים עֶשְׂרִ֑ים רְחֵלִ֥ים מָאתַ֖יִם וְאֵילִ֥ים עֶשְׂרִֽים׃
Two hundred she-goats and twenty he-goats; two hundred ewes and twenty rams.
Torah Temimah points to Bereshit Rabbah 76:7 (and parallel in the Bavli on mating ratios).
Sefaria · Bereshit Rabbah 76:7
א"ר אליעזר: כדרך הארץ שלח לו, עזים מאתים ותישים עשרים – חד לעשרה; רחלים מאתים ואילים עשרים – חד לעשרה.
Rabbi Eliezer said: He sent to him according to the way of the world: two hundred she-goats and twenty he-goats — one for ten; two hundred ewes and twenty rams — one for ten.
The Midrash notes that Yaakov’s gift proportions reflect natural mating ratios: one male for ten females among goats and sheep.
Derash on the numbers (Bereshit Rabbah) — practical observation of natural ratios.
Yaakov arranged the gift according to the ordinary ratios of males to females in the flock.