Major Rawls explains to Robbie that by taking responsibility for the 13 bodies found in the crate, his clearance rate would go from 51.6% to 39.4%. Those numbers cannot be accurate, at least not down to the nearest tenth of a percent. Working backwards, Rawls had 42 cases already and if he had cleared 22, the percentage would be 52.4%, for 21 it would be 50% exactly. Since he stated he had over 50%, he probably solved 22. By adding 13 cases and if none of them can be cleared, his new ratio would be 22 out of 55, exactly 40%, not 39.4%. It is possible he was just fabricating the numbers to make his point so as to not take on the additional workload.