"output?"

This says that the way that growing the input by a factor of $x$ changes the input is exactly the opposite from the way that shrinking the input by a factor of $x$ changes the input\. In terms of the "communication cost" interpretation, if doubling \(or tripling, or $n$\-times\-ing\) the possibility space increases costs by $c$, then halving \(or thirding, or $n$\-parts\-ing\) the space decreases costs by $c.$

output?