Abstract: Recently the existence of a new quantity which decreases along RG-flows of 4d supersymmetric QFT's with R-symmetry has been conjectured. I will analyze this conjecture from a dual supergravity perspective: using some general properties of domain-wall solutions dual to R-symmetric RG flows, I will define a function interpolating between the correct values at the UV and IR fixed points. I will finally test its monotonicity properties in a class of examples.