Using the 4 sq ft per bird, your 4x6 coop = 24 sq ft which should comfortably hold 6 birds. Your run is 150 sq ft which would be adequate for a dozen or so birds but you really have to go by what you can fit into your coop.
I think that four sq. ft. is pushing it if your weather keeps the birds inside; I've got almost five sq. ft. in my coop, and some of my birds are bantams, and it can get tense in there if the weather's bad in winter. Mary
What is your climate? How are you going to manage them? Will they always have access to the run or will you lock them up at night and for part of the day? Will weather or your schedule allow them access to the run at all times? Will you ever integrate new chickens? Will you let a broody hen hatch or raise chicks with the flock? Are they full sized or Bantam? How hard do you want to work? How do you plan to manage the poop?
You can follow the link in my signature to see my thoughts on space, but I’d have to know a whole lot more about your situation before I’d even hazard a guess as to how many chickens you should get. If they have access to that run whenever they are awake you have room for more than if they are locked up part of the time they are awake. You are not limited by your coop by itself. You are limited by how much room they have available when they need it.
I dont have a rooster so no hens setting.i live on the coast of NC so i don't think i will need to close them in the coop.
I have a top on half the run and they can go under the coop it's 24" off the ground.i have red star and barred rock hens
I have a door at both ends of the coop with a poop tray and staw.i use it in my compost.
That's a roof on half the run.net on other half.automatic feed and water. The feed and water are in the run.
The coop is only for them to roost.i have 4 laying box's but can add more.