Dark Matter constitutes 85% of the matter in the universe, yet its mass remains unknown. The Selection-Stitch Model (SSM) identifies Dark Matter not as a new exotic field, but as a ”Failed Proton”—a topological knot that failed to anchor to the vacuum lattice. We derive its base mass as pure volumetric displacement (Mvol = 1728me ≈0.88 GeV). Crucially, we resolve the cosmic abundance ratio by deriving a specific ”Chiral Oscillation Correction.” By identifying the Figure-Eight knot (41) as an amphicheiral structure that tunnels between two mirror states, we calculate the oscillation cost as exactly two units of surface energy (2K2). This yields a corrected mass of Mtot = 2016me, predicting a cosmic ratio of ΩDM /Ωb ≈5.49, matching Planck observations to within 1.6%.