Can a hen hatch chicks outside in garden in small coop?

I agree with the other two responses. 4 days is a little too early for you too really notice. Now assuming that they are fertile, you should see the outlining a small little chick when you check again on day 10. If you don't see anything by that time they are duds and will not hatch so discard them. Also mark the eggs that are under you broody hens, chances are if you have other egg laying hens they will try to lay their eggs in that spot. So everyday check and remove any that added. I've had 5 hens that have hatched their chicks out side one hatched it under the stairs and the rest inside of the coop. You wanna make sure that the place that she is brooding is protect from the elements. The chicks will hatch on day 20-22.