Managing ads (site owners)
From a space's manage page, Edit settings lets you change its name, price, max advertisers, and auto-accept setting. Size is fixed once created. Lowering the max advertisers never removes anyone already running — it just stops new ones joining until the numbers drop naturally. Raising it immediately offers the new slot(s) to whoever's waiting in the queue.
Changing the price only applies to new advertisers — anyone already running keeps the rate they agreed to.
You can delete a space entirely, but only once nothing is pending, awaiting payment, or live on it — otherwise deleting would pull paid ads with no warning. Take those down first.