Recent developments in analytical methods have introduced jet substructure observables accurate beyond leading-logarithm accuracy. One recent ATLAS publication based on 32.9 fb −1 of √ s = 13 TeV **data** presents a first measurement involving the jet soft-drop mass -one such substructure variable -using dijet events from p-p collisions [38]. The analysis features a reclustering of the constituents of anti−k T jets based on a designated soft-drop mass procedure. This procedure is based on an iterative condition which is governed primarily by the choice of two parameters: z cut and β , which relate to p T and angular thresholds in the context of gluon radiation. The final results correspond to normalized differential cross-section measurements, presented as a function of the logarithm of the dimensionless quantity ρ 2 , where ρ is the ratio of the invariant mass of the jet following the soft-drop procedure and the transverse momentum of the ungroomed jet (ρ = m soft drop /p ungroomed T ). The inclusion of p ungroomed T in the denominator counters an undesireable p T dependence. The distribution shown in Figure 7b, corresponding to the particular choice of β = 0, can be contrasted with other such distributions (for β = 1, 2) in the original publication. An unfolding procedure is used to correct for detector-level effects. The evolution of the distributions with β and z cut highlights particular regions of the quantity log 10 ρ 2 with larger levels of disagreement between **data** and predictions. Such disagreements between the measured **data** and either precise QCD calculations or leading-logorithm Monte Carlo simulations will prove beneficial in improving our understanding of the collinear QCD regime.