Time-evolving observer frame photon spectrum without absorption on extragalactic background light (top panel) and electron distribution (bottom panel) from the forward shock with the same photon injection term as in Fig. 2. The other simulation parameters are E₀ = 1.4 × 10⁵⁵erg, n₀ = 3 cm^-3, ϵ_e = 0.8, ϵ_B = 10^-8, Γ₀ = 450 and s = 2.4. The redshift is z = 1.8. The black and red long-dashed lines show the photon and electrons distributions at t = 0.1 s and t = 10 s without pair production, and the positron distribution at t = 0.1 s is presented by a solid magenta line in the bottom panel.