The main atonement offered by a sacrifice is brought about by sprinkling – called a matanah (placing) – the blood of the sacrifice on the altar. The matanah was done differently depending on the sacrifice. A regular korban olah would have the blood sprinkled on two corners of the altar so that it would splash on two sides each time, in order to assure that all sides of the mizbe’ah (altar) had gotten blood on them (shetei matanot she-hen arba = two “placings” that are four).
The altar had a red line running around it called the hut ha-sikra which indicated the upper and lower halves of the mizbe’ah. In the case of the olah described above, the blood was sprinkled on the lower half. In the case of an animal that was brought as a sin offering, the blood would be sprinkled on the top of the altar, near each of the raised corners, where each side was sprinkled once (arba matanot = four “placings”).
Rabbi Shimon Ish HaMitzpa suggests in our Gemara that the blood of the daily sacrifice – the olat tamid – should be put below the hut ha-sikra with two separate matanot, almost a compromise position between the ordinary olah and the hatat.
To contrast this placing of the blood, the Gemara points to a Mishna later on in Massekhet Yoma (53b) which describes how the Kohen Gadol entered the Holy of Holies and sprinkled the blood towards the kaporet covering the aron (ark) “one upwards and seven downwards.” In that case there was no strict line demarcating the difference between the upper and lower halves, and the Gemara explains that he sprinkled the blood ke-matzlif. The Me’iri explains this expression as meaning that he placed the blood without paying particular attention to whether they were directly above or below one another. Another explanation given by the Tosafot ha-Rosh suggests that the difference was the direction in which the Kohen Gadol held his hand – whether he held it upwards or downwards.