We present a lattice QCD calculation of the ΔI ¼ 1=2, K → ππ decay amplitude A 0 and ε 0 , the measure of direct CP violation in K → ππ decay, improving our 2015 calculation [1] of these quantities. Both calculations were performed with physical kinematics on a 32 3 × 64 lattice with an inverse lattice spacing of a −1 ¼ 1.3784ð68Þ GeV. However, the current calculation includes nearly 4 times the statistics and numerous technical improvements allowing us to more reliably isolate the ππ ground state and more accurately relate the lattice operators to those defined in the standard model. We find ReðA 0 Þ ¼ 2.99ð0.32Þð0.59Þ × 10 −7 GeV and ImðA 0 Þ ¼ −6.98ð0.62Þð1.44Þ × 10 −11 GeV, where the errors are statistical and systematic, respectively. The former agrees well with the experimental result ReðA 0 Þ ¼ 3.3201ð18Þ × 10 −7 GeV. These results for A 0 can be combined with our earlier lattice calculation of A 2 [2] to obtain Reðε 0 =εÞ ¼ 21.7ð2.6Þð6.2Þð5.0Þ × 10 −4 , where the third error represents omitted isospin breaking effects, and ReðA 0 Þ=ReðA 2 Þ ¼ 19.9ð2.3Þð4.4Þ. The first agrees well with the experimental result of Reðε 0 =εÞ ¼ 16.6ð2.3Þ × 10 −4. A comparison of the second with the observed ratio ReðA 0 Þ=ReðA 2 Þ ¼ 22.45ð6Þ, demonstrates the standard model origin of this "ΔI ¼ 1=2 rule" enhancement.