Based on the date (2013), I assume this figure was made before the Higgs was discovered or its mass was published. The curves are based on a theoretical calculation of the various branching ratios as a function of the Higgs mass within the Standard Model. If the branching ratios are also measured then this would be a way to measure the Higgs, or at least one can check the consistency of the measured Higgs mass and branching ratios, with the Standard Model prediction.
There is not a direct coupling between the Higgs and 4 leptons in the Standard Model. I believe the decay process you have in mind is $H\rightarrow ZZ \rightarrow 4\ell$ (Higgs decays to two $Z$ bosons which decay to a set of 4 leptons, either electrons or muons). (As @joseph h mentions in the comments, there are also other decay modes that lead to 4 leptons, like $H\rightarrow WW \rightarrow 4\ell$ and $H\rightarrow t\bar{t}\rightarrow 4\ell$). The four leptons are stable enough to be directly detected. However, I believe this plot is showing direct decays of the Higgs into other particles, ignoring the future decays that will occur before the final products are seen in a detector.
I can't be 100% sure about what message this plot was intended to send without additional context, though (like, what paper was it published in).