In a ovary with 100 ovules ready for fertilisation, how may megaspores fail to form embryo sacs?

Ovary with 100 ovules has 100 megaspore mothers cells i.e. one in each ovule. Each megaspore mother cell undergoes reduction division and forms four megaspores. Out of four only one is functional and the remaining three degenerate. In 100 ovules  a total of 100 X 3 megaspores = 300 ovules degenerate.