I think there's a mistake in the article, a fertility rate of 0.87 children per woman does not give 8 grandchildren per 100 taiwanese, but 100x0.87x0.5x0.87x0.5

I think there's a mistake in the article, a fertility rate of 0.87 children per woman does not give 8 grandchildren per 100 taiwanese, but 100x0.87x0.5x0.87x0.5=19 grandchildren per 100 taiwanese.