AZ: It does seem the point is lost on you so we will not rehash. However, the example we used, for simplification was 105 births of boys per YEAR. SO yes, basic math dictates every year there are 105 births multiply that by the amount of years provides the answer.
What does amaze me that if there are more boys than girls at age 18. No matter how many years pass by the result is the same. There will always be more boys than girls society.
As you mentioned, someone else would need to explain that you can not have 1890 boys marry 1000 girls an still have an issue where there are not enough boys.