Congrat! Can't wait to see pics of the babies :)
That's a very nice broody box - she will enjoy hanging out in it with her chicks once they hatch. You will want to add some hardware cloth to the lower sides unless you've already done that.
As far as how many eggs - it depends on the initial size of your broody and temperatures where you live - because they will rotate the eggs in/out and around in the nest to get the best hatch. They can really flatten themselves out to cover up as many eggs as possible - but if they can't rotate them in and out of warmer weather, some may get delayed in development and then not hatch.
My Smokey is a smaller LF EE and she had 8 under her - only 3 hatched even though I believe at least 7 were viable when I put them under her. However, it was still winter here so temps fluctuated between 20s to 40s at night AND they were shipped eggs with which I've never had better then 50% hatch rate. So that could have made a difference. Still I don't think I would put more then 6 under her next time. However, when my Lavender Orpington's go broody I could probably slip a dozen under one of them as they are HUGE!
Here's a pic of Smokey before she hatched her babies.

Quote:
Originally Posted by
kevlar 
Hello to all you fans of broody hens. I have been keeping chickens since last summer and have definitely caught the chicken bug or addiction lol. We had fourteen chickens total and the first Two birds we got turned out to be roosters. We ate One and decided to keep one just to piss of the neighbors lol. Well recently One of my hens decided to go broody she kinda toyed with it for a few days sitting in the nest all day and squawking at me when I went to check for eggs, but then sleeping on the roost at night. I decided to give this broody thing a try, I gave her a bunch of fake eggs to sit on and four days ago I went out to check on her after dark and she had decided to stay in the nest full time. Great now I need to learn all about broody hens but byc is a great resource for learning and now I can also share my experience so yay byc!!! I built her a broody box out by modifying a dog crate and building a stand for it so I don't loose and square feet of the coop. I moved her in to the box on to her new nest last night and she was still on her nest in the morning! I was in and out of the coop all day and she did get out to stretch her legs and take a massive poop. She is still on her nest and we are well in to night Two in her new nest. Since we have a young stud of a roo in our flock and we only have Eleven hens I'm pretty sure most of my eggs are fertile, I have been saving all the nicest looking Ones for the last Three days and was thinking about setting a clutch tomorrow. I'm not sure how many to set I was thinking somewhere between Ten and Fifteen? My Wife said Three but I'm definitely going to set more than that lol.
here is the set up I built her, I will post pics of her in the coop tomorrow 

Oops I thought i had a more complete pic I built a better nest box and lined the bottom with hardware cloth