The background-screening simulation multiplies population by base rate, then applies stage-one sensitivity and false-positive probability. In an illustrative ten thousand population with prevalence point zero zero one, there are ten assigned threats and nine thousand nine hundred ninety others. Sensitivity point nine five gives nine point five true flags; specificity point nine nine gives ninety-nine point nine false flags. Both bars count expected flagged cases at five pixels per case. Fractional counts are expectations, not identified people. Stage two is applied only to stage-one flagged cases. Using illustrative nine point five true flags and ninety-nine point nine false flags, sensitivity point nine eight leaves nine point three one true flags. Specificity point nine nine five leaves point four nine nine five false flags. Both bars count final expected flags at fifty pixels per case. The source multiplies the stage likelihoods directly. Its entered rates do not establish independence or measured performance of a real vetting protocol. The written system false-positive field sums stage-one and stage-two false flags before dividing by the non-threat population. For illustrative ninety-nine point nine and point four nine nine five, the numerator is one hundred point three nine nine five. Final retained false flags alone are point four nine nine five. Both bars show expected counts at five pixels per case. The source field therefore counts overlapping stages rather than simply final false alarms; preserve that distinction when interpreting its report and do not treat it as validated security effectiveness.