You are forgetting about winter. They won't go out much during winter.
My coop (8 x 12 with an 8 x 4 room with the nest boxes and a built-in brooder) with attached fully secure run (28 x 12 with 8 x 4 extension) houses 27 birds. I never close the pop door between the coop and run.
I'm not sure why you want to cram that many chickens in there. The rule of thumb is 1 chicken for every 3-4 sq feet. You've got 160 sq ft which comes to 40 chickens on the roomy side and 53 chickens on the "a bit crowded" side.
So with those more realistic numbers I wouldn't put more than one...