I haven’t used it myself, but was posted by someone on a Mexican forum I follow, who has had total success with it.
I don’t know that you would have to put multiple ones in a 12x12 room- it seems like the ants would be attracted to it because of the sugar, just as they would make a beeline for a pile of cookie crumbs. Ants don’t just wander around aimlessly looking for things they like- they have a hive mind and if there is some attractant, they will all go to it.
But it would seem most logical to place the bait closest to where the ants are entering, i.e doors or windows.
There are lots of ants where I live, but in my experience, they don’t come in the house to any great extent unless they have a specific purpose for doing so- either food or food residue, or in the case of some big black ants we have here, to find a place to hide and care for their eggs.
My cleaner found scores of those ants, with hundreds of eggs, under the couch cushion which sits on a concrete platform and I found the same thing going on in a wooden box I keep boardgame pieces in.
When I see random ants of those type running around inside, as opposed to a trail of ants, I know those are the scouts, looking for a hidey hole to deposit and tend their eggs.
Another time there was an ant invasion that was horrific, like some biblical plague. I was upstairs and a friend who was staying with me started screaming downstairs. There was a swath of large ants, almost a meter wide, and coming and coming with seemingly no end to the army. Millions of them. They were swarming up my terrace steps, up and over the dining table out there, through the kitchen door, across the kitchen, up the cupboards and out the window.
Within 10 minutes there was no sign of them- they were just passing through, taking a shortcut to wherever they were headed.
As a host, I wouldn’t want ants in the house, as it’s cause for guest freak-out and bad reviews. But when I’m here alone, ants that come in to eat crumbs or gather around a food spill don’t bother me at all- they don’t carry disease and I consider them to be nature’s cleaners. They feast and leave.
Of course, if they are biting, stinging ants, and you need to remove them, that’s a pain, literally.