John Gill Commentary Genesis 46:18

"These are the sons of Zilpah, whom Laban gave to Leah his daughter; and these she bare unto Jacob, even sixteen souls." — Genesis 46:18 (ASV)

These [are] the sons of Zilpah, whom Laban gave to Leah his
daughter
To be her maid, when she was married to Jacob, by whom he had Gad and Asher:

and these she bore unto Jacob, [even] sixteen souls ;
not that Zilpah bore sixteen children to Jacob, for she bore but two; but the children and grandchildren of these two with them made sixteen.