The **data** weighting method described above neglects the differences in momentum scale and resolution between standard and charge-flip electrons. This approximation was validated by recomputing the expected SR yields after reducing the p T of the electron with largest |η| by 5 GeV -a value bounding from above the invariant mass resolution of same-sign ee pairs near the Z boson mass -in all weighted **data** events, which was found to have a negligible impact on the results. For the Rpc3LSS1b SR, the method is adapted by simply selecting **data** events with three or more leptons, which are weighted by the probability of one or more electron charges to be mismeasured such that the resulting event contains three same-sign leptons.