When deciding how many hatchling bins I needed I considered how many females I have, or plan to have breeding in the current season. For example; if I have 10 breeder females, I assume each female will produce between 4 - 10 eggs. so I would need between 40 - 100 bins. I assume that I will be rid of some hatchlings before others hatch, but to be on the safe side I use this formula.

X - Y = Z/2
X = 100
Y = 40

100 - 40 = Z/2
60 = Z/2
60/2 = Z
30 = Z

THEREFORE

X-Z = A

A = the number of bins I should have

100 - 30 = A
A = 70

If I have 10 breeder females I will need 70 bins to be on the safe side, but you could probably get away with fewer bins.

Hope this wasn't too confusing.