In a recent experimental paper [Bid et al., Nature 466, 585 (2010)] a qualitative confirmation of the existence of upstream neutral modes at the ν=23 quantum Hall edge was reported. Using the chiral Luttinger liquid theory of the quantum Hall edge we develop a quantitative model of the experiment of Bid et al. A good quantitative agreement of our theory with the experimental data reinforces the conclusion of the existence of the upstream neutral mode. Our model also enables us to extract important quantitative information about nonequilibrium processes in Ohmic and tunneling contacts from the experimental data. In particular, for ν=23, we find a power-law dependence of the neutral mode temperature on the charge current injected from the Ohmic contact.