Software development, hardware development, engineer dispatch, and personnel consulting

I noticed the fan when I went for lunch at Jonathan`s coffee & restaurant.
The fan said “Do not take it away.”(though it is supposed to be a sale promotion) Most of the sales promotion goods to make us cool to save on electricity are out of stock.
Saving on electricity affects those things, doesn’t it?
I wonder what sales promotion goods which are forbidden to be taken away mean. (I)