The generally accepted number for coops is 4 sq.ft. per bird so 8 would be the max. I can't imagine that 15 in that size coop would work out very well.
You really should start your own thread but that will never work for 5 chickens. It's entirely too small. Approximately a 20 sq.ft coop and 50 sq.ft. run will be required for your 5.