Similar to Fig. 11, with an ambient cloud extinction of 2 mag. HDO/H₂O (f_D1) and D₂ O/HDO (f_D2) ratios toward three protostars in the simulation, with similar final mass of ~ 0.7 M_⊙. Tracer particles are binned according to the time at which they reach the hot corino, in bins with a width of 50 kyr. Time corresponds to the time after the onset of collapse, t₀. Each bar shows the median values of tracer particles accreted in the time interval, and the error shows the [15.9, 84.1] percentiles. The number of tracer particles within each bin is denoted in blue above the first row.