That's 3.9 square feet.
And the 10 square feet in the run is exactly the size of the common fiberglass drop-in tub-shower combo that you see in so many manufactured homes.
So the minimums for one chicken amount to a large bathmat next to a guest shower.
From an article I'm working on:
But I free range/have a huge run and my chickens only use the coop to sleep and lay eggs! Why do I need all that space inside?
You might not. As I've said, these are guidelines, not hard-and-fast rules.
If you never close the pop door so that your coop and run...