What does Genesis 30:10 mean?

Leah was given Zilpah as a wedding present by her father (Genesis 29:24), on the night he treacherously snuck Leah into the marriage bed, rather than Jacob's intended bride, her younger sister Rachel (Genesis 29:21–26). Unsurprisingly, though Jacob was able to marry Rachel almost immediately afterwards, he has no meaningful love for Leah (Genesis 29:31). Despite that fact, Leah was able to bear sons for Jacob while Rachel remained barren. To resolve this, Rachel used the cultural approach to servants to have children "by proxy," using her servant Bilhah to birth two sons for Jacob (Genesis 30:1–8).

In the meantime, Leah has stopped bearing children, but she wants to continue to give sons to Jacob (Genesis 29:35). Apparently, Leah agrees with Rachel that this is a competition, and she intends to win. So Leah follows her sister's example, and gives Jacob her servant girl Zilpah as a wife, planning to claim any babies born to their union as her own. Zilpah eventually has had a son, Jacob's seventh boy, who will be named Gad, to reflect what Leah sees as good fortune.