what is the point of that calculation if you base it on some bogus birth ratio and other imaginary factors?
also if you talk about dolcett world as I know those women are like all overgrown toddlers only 3-4 years old

if you want to do such calculations it is better to do it from other direction
if we assume that the max rate woman can give births is once a year you can kill a bit less than the number of fertile women in existence per one year still maintaining the population.

if we assume that women become fertile from age of 10 to 50 (ignoring everyone older as they will neither die or give birth) this will be no more than 80% of total population of women every year

it does not matter at what age they are getting killed and other factors as long as you maintain overall number of kills.

However, from the technical perspective, this is a bit complicated, because every family will need to have more than 10 girls if they want to do snuffing once a year simply because of their slow growth rate