Critical magnetic field $B_{\varphi ,\mathrm{crit}}$ (Eq. (20)) in the numerical simulation depending on the wavelength of the Tayler instability for several resolutions with the numerical viscosity and resistivity estimated with the simulation grid size (Eq. (44)). The Tayler instability should be unstable in the simulation when the critical field is weaker than the magnetic field in the GRMHD simulation (gray region for Δx = 12.5 m).