Corrected invariant mass spectrum for the coherent four-pion photoproduction fitted with two resonances plus a non-resonant continuum, Eq.A.3.. Black error bars represent the statistical uncertainty, the orange band shows the uncorrelated systematic uncertainty, and the boxes show them added in quadrature. "Prob'' reflects the probability of obtaining the given or a higher $\chi^2/\mathrm{ndf}$ of the fit.