What does Genesis 30:19 mean?

Jacob found himself married to two sisters in the span of a week, one of whom—Leah—he had been tricked into taking due to deception by their father (Genesis 29:18–30). Partly due to that fraud, Jacob is said to have hated Leah, while preferring his only intended bride, Rachel. God responded to Leah's pain by allowing her to bear children while Rachel remained barren (Genesis 29:31–35). This began a fertility competition, where Rachel eventually used her servant girl to give Jacob sons, and Leah followed suit (Genesis 30:1–13). Rachel, who had apparently convinced Jacob to stop having sex with Leah, trades one night of Jacob's attention for some fertility-enhancing mandrake roots. As a result, Leah conceives her fifth natural son, accordingly named Issachar, a reference to "wages" (Genesis 30:14–18).

Now we learn that Leah has given birth to her sixth naturally-born son. Counting the sons born to her servant Zilpah by Jacob, Leah now claims eight boys as her own. This son is the tenth born to Jacob by three different women. Rachel has yet to give birth to any children of her own.