Neural network TEV predictions for HO (blue, left) and HO (red, right) validation data. The x-axis represents an arbitrary index number of a data point. The scattered points represent the difference between the known terminal velocity (v_true) of each synthetic spectra and the velocity predicted by the network (v_exp). The horizontal black lines indicate ±0.03 km s⁻¹ : the fraction of points enclosed in this region is 95% for HO and 96% for HO. The shaded colored region indicate a 1σ error on the predictions: 0.017 km s⁻¹ for HO and 0.015 km s⁻¹ for HO.