1step,rule,n_before,n_after,n_removed,rationale21,data lines read (excluding header),1200,1200,0,all non-header lines of sales.csv32,"drop lines that cannot be parsed unambiguously (CSV field count != 5, sale_id not S+5 digits, unknown municipality, invalid ISO date, non-numeric price/area)",1200,1164,36,corrupted/garbled export lines; content not reconstructed per task rules43,drop records whose sale_id is duplicated,1164,1164,0,sale_id must be unique; duplicates would be ambiguous5