At first, the graph you show is not BET analysis!!! The dependence of Adsorbed quantity vs Relative pressure (P/Po) is ADSORPTION ISOTHERM!!! Data from adsorption isotherm in the range of relative pressure of 0.05 - 0.30 are used for BET-isotherm, by which specific surface area (in m2/g) is calculated. Very roughly on the base adsorption isotherm, your sample cold have surface area about 230-240 m2/g, but it is necessary to calculate it by standard BET-isotherm. But, it is only one physical characteristic, nor shape of adsorption isotherm neither surface area are not directly connected with catalytic properties. Of coarse, the higher is surface area, the higher is the probability of catalytic activity (because heterogeneous catalytic reaction proceeds on the surface of heterogeneous catalysts). You must have catalytically active centers on surface (for cracking reaction probably acidic) that you need to determined by another method (TPD of ammonia, FTIR spectra of adsorbed pyridine, ...)