My wife is getting pretty good at chicken math. Originally she wasn't - kept trying to tell me that 26 chickens was "enough," whatever that is supposed to mean...
Then she said, well, since it's Spring and the hens are now a year old, maybe we can get a few chicks - thinking in the right direction, but then she'd say something foolish like "but only four more, 30 chickens is enough..." again with that word!
But then she had a breakthrough. Coincidentally this occurred just after the broody Sussex hatched out four new chicks to go with the four we bought to put under her. Suddenly, she began to do sums correctly! Today, for example, we brought home another 8 chicks, to put under the other broody, who has hatched two and has two more eggs under her. And we still have one broody hen, so...
Of course the ones hatched out at home don't count, because as everyone knows, they will all be cockerels, which don't count because they all end up in the freezer. (Unless they are really sweet and cute.)