Their mode of fertilization is external.
They lay eggs in the water and there is a chance of destruction of these gametes by water current if they are in less quantity.
So they lay more and more eggs in order to rule out the possibility of destruction of all eggs.
Thus at least some eggs are fertilized by sperm and produce zygote.
Several of them are outside the normal range the Normal range is like 50 but if you could re-write the question I will help but I think 5th percentile is low so that's my best answer.
