Equilibrium adsorption in micropores is treated using a finite single-cell statistical model. The micropore space is represented as an ensemble of statistically equivalent independent cells of finite capacity. The state of a cell is specified by the discrete number of adsorbed molecules. The configurational constraint is introduced through the free volume of the cell, V_free(i) = v_c - iβ. The adsorption isotherm is obtained from the finite partition function over the admissible cell states. The same statistical sum gives the state probabilities, mean cell loading, loading variance, calculated adsorption, saturation limit, Henry limit, monotonicity, and response identity. The Langmuir isotherm is recovered as the exact single-occupancy special case of the finite-cell statistics. The model is evaluated for CO₂ adsorption on zeolite NaY NIST RM 8850 using 48 published equilibrium adsorption points. The pressure-based variable is x = K(T)p. The calculation uses nominal temperature branches of 298.06, 333.06, 353.05, and 393.00 K, with pressures from 0.027 to 3.018 MPa. The fixed structural quantities are v_c = 958.2 ų, ω = 14, and ν_mi = 0.358 cm³ g⁻¹. The corresponding conversion factor is 0.6204059549658079 mmol g⁻¹ per unit mean cell loading, and the structural limiting adsorption is 8.686 mmol g⁻¹. The fitted CO₂ parameters are K0 = 0.0013229 MPa⁻¹, E_ads = 33.675 kJ mol⁻¹, and β = 57.542 ų. For the full 48-point array, the mean absolute error is 0.0361 mmol g⁻¹ and the root-mean-square error is 0.0539 mmol g⁻¹. For the pressure range p ≥ 0.25 MPa, the mean absolute error is 0.0158 mmol g⁻¹ and the root-mean-square error is 0.0228 mmol g⁻¹. The largest normalized residuals occur in the low-pressure region. These residuals define the applicability boundary of the statistically equivalent single-cell approximation. Description of this region requires an extension to a heterogeneous cell ensemble or an affinity-parameter distribution. This record contains the main manuscript and the Supporting Information. The Supporting Information gives the complete numerical array used to reproduce the calculation. For each experimental point, it reports the affinity variable, admissible cell states, state weights, state probabilities, cell moments, calculated adsorption, residuals, normalized residuals, and internal consistency checks.