When the kohen burns the bird on the altar, in its removed separate body parts, from crop to gizzard. Plus, the examples of when the intent was wrong or the placement was wrong, and so on - and when those errors in protocol invalidated the offering, distinguishing between the sin-offering and the burnt-offering. Also, If the kohen didn't remove the crop, or other parallel removings, then, with implications for whether the offering is supposed to be a sin-offering or burn-offering. With a key dispute and 3 understandings of that particular dispute.