I suspect it was a work around to a proposal for a flat prohibition after someone with a bigger lot that had or wanted animals pushed against the prohibition...
Basically they will allow those limited animals if your yard is big enough to accommodate a detached 7000 sq/ft pen or building... No small run or coop, you would need to designate a 7000 sq/ft area for the chickens, and then be limited to 12 birds per each 7000 sq/ft designated area... I also...