In my original post I did accidentally write X chromosome when I meant Y. Sorry about the typo.
Jackson, I got the cell divisions directly from the Myers’ blog:
In the case of females, this number [of mutations] is about 30, which means that each of a females eggs is the product of 30 cell divisions from the time the zygote was formed (Vogel and Rathenberg, 1975). Human females have about 500 eggs. In males, the number of cell divisions leading to mature sperm in a 30 year old male is about 400 (Vogel and Motulsky, 1997). This means that about 9 mutations (0.3 × 30) accumulate in the egg and about 120 mutations (0.3 × 400) accumulate in a sperm cell. Thus, each newly formed human zygote has approximately 129 new spontaneous mutations.
*writing in bold added by me