Nothing. There is no 8th.
“Now, sirs,” I said, “it is possible for us to show how the eighth day possessed a certain mysterious import, which the seventh day did not possess, and which was promulgated [intimated] by God through these rites.” … “The command of circumcision, again, bidding the Jews always circumcise the children on the eighth day, was a type of the true circumcision, by which we are circumcised from deceit and iniquity through Him who rose from the dead on the first day after the Sabbath, [namely through] our Lord Jesus Christ. For the first day after the Sabbath, remaining the first of all the days, is called, however, the eighth, according to the number of all the days of the cycle, and remain the first.” … “You know, then, sirs, ” I said, “that God has said in Isaiah to Jerusalem: ‘I saved thee in the deluge of Noah.’ By this which God said was meant that the mystery of saved men appeared in the deluge. For righteous Noah, along with the other mortals at the deluge, i.e., with his own wife, his three sons, and their wives, being eight in number, were a symbol of the eighth day, wherein Christ appeared when He rose from the dead, for ever the first in power. For Christ, being the first-born of every creature, became again the chief of another race regenerated by Himself through water, and faith, and wood, containing the mystery of the cross; even as Noah was saved by wood when he rode over the waters with his household.”
Justin Martyr - Dialogue with Trypho 24:41:138. [A.D. 160].