Charles Ellicott Commentary Leviticus 16:14

"and he shall take of the blood of the bullock, and sprinkle it with his finger upon the mercy-seat on the east; and before the mercy-seat shall he sprinkle of the blood with his finger seven times." — Leviticus 16:14 (ASV)

And he shall take of the blood. —Having left the Holy Place and returned to the court, where the priest stood with the bowl of the blood of the bullock, stirring it to prevent it from coagulating , the high priest took it and went back to the Holy of Holies, to the same place where he stood on his first entry.

Sprinkle it with his finger. —During the Second Temple, the high priest sprinkled the blood once upwards and seven times downwards, in such a manner that the eight sprinklings formed a continuous line on the ground. As he sprinkled, he was obliged to count one, two, three, etc., so that he would not make a mistake.