Charles Ellicott Commentary 1 Samuel 1:24-25

"And when she had weaned him, she took him up with her, with three bullocks, and one ephah of meal, and a bottle of wine, and brought him unto the house of Jehovah in Shiloh: and the child was young. And they slew the bullock, and brought the child to Eli." — 1 Samuel 1:24-25 (ASV)

With three bullocks ... And they slew a bullock. — At first sight, there seems to be a discrepancy here, and the Septuagint translators seem to have perceived it, for they read “a bullock of three years old” instead of “three bullocks.” The true explanation, however, is that the one bullock alluded to in 1 Samuel 1:25 was the burnt offering by which the child was consecrated to the Lord. The other two were for the yearly festival offering; since their presentation was the usual gift, the chronicler did not think it worthwhile to mention them here again.